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-version 1.28, 2025/04/18 19:43:18
+version 1.45, 2025/05/05 12:34:02
  Line 4
  @settitle The FreeM Manual
  @copying
- This manual is for FreeM, (version 0.64.0-rc0), which is a free and open-source implementation of the M programming language.
+ This manual is for FreeM, (version 0.64.0-rc1), which is a free software implementation of the M programming language.
+ Print-optimized versions of this book are typeset in @emph{Computer Modern} by the author using the @emph{GNU Texinfo} tools.
  Copyright @copyright{} 2014-2025 Coherent Logic Development LLC
- Line 18  Permission is granted to copy, distribut
+ Line 19  Permission is granted to copy, distribut
  @title The FreeM Manual
  @subtitle @sc{The Official Manual of FreeM}
- @subtitle Version 0.64.0-rc0
+ @subtitle Version 0.64.0-rc1
  @c@vskip 10pt
  @c@center @image{freem-logo-sm,,,,.png}
  @author Serena Willis
- Line 42  This is the official manual for the Free
+ Line 43  This is the official manual for the Free
  @menu
  * Introduction::                        About the FreeM Project, its history, and its goals.
+ * Document Conventions::                Conventions used in this manual.
+ * A Note on Standards::                 FreeM positioning regarding the M Development Committee.
  * FreeM Invocation::                    How to invoke FreeM from the command line.
  * The FreeM Environment Daemon::        Managing shared resources in the FreeM environment.
  * The FreeM Direct-Mode Environment::   Executing M programs interactively.
+ * Debugging::                           The program development cycle of FreeM.
  * Directives::                          Per-Routine Language Directives.
  * Intrinsic Special Variables::         Intrinsic Special Variables.
- Line 73  This is the official manual for the Free
+ Line 77  This is the official manual for the Free
  * Global Aliasing::                     Defining alternate names for globals.
  * Global Mappings::                     Mapping global names to non-default namespaces.
- * Transaction Processing::              Transactions in FreeM.
  * Asynchronous Event Handling::         Handling asynchronous events in FreeM.
  * Global Triggers::                     Responding to global accesses in M code.
  * Synchronous Event Handling::          Synchronous events in FreeM.
- Line 92  This is the official manual for the Free
+ Line 95  This is the official manual for the Free
  * Interrupt Handling::                  How FreeM handles interrupts.
  * Error Processing::                    How to handle errors in M program code.
  * FreeM Error Codes::                   Explanations of each FreeM error code.
- * Debugging::                           The program development cycle of FreeM.
  * System Configuration::                Configuring your FreeM installation.
  * Accessing FreeM from C Programs::     How to use the mlib interface.
- Line 110  This is the official manual for the Free
+ Line 112  This is the official manual for the Free
  @node Introduction
  @unnumbered Introduction
- FreeM started its life as @emph{FreeMUMPS}, written for MS-DOS and ported to SCO UNIX by a mysterious individual going by the name of "Shalom ha-Ashkenaz". It was released to MUG Deutschland in 1998. In 1999, Ronald L. Fox ported FreeM to the Red Hat Linux 5 of the GNU/Linux operating system. Thereafter, maintenance was taken over by the Generic Universal M Project, which changed its name first to Public Standard MUMPS and then by popular request to FreeM.
+ FreeM started its life as @emph{FreeMUMPS}, written for MS-DOS and ported to SCO UNIX by a mysterious individual going by the name of "Shalom ha-Ashkenaz". It was released to MUG Deutschland in 1998. In 1999, Ronald L. Fox ported FreeM to the Red Hat Linux 5 distribution of the GNU/Linux operating system. Thereafter, maintenance was taken over by the Generic Universal M Project, which changed its name first to Public Standard MUMPS and then by popular request to FreeM.
  When GT.M was open-sourced in late 1999, FreeM and GUMP were essentially abandoned. L.D. Landis, the owner of the original GUMP SourceForge project, and one of FreeM's significant contributors, passed maintenance of FreeM and ownership of its SourceForge project to Serena Willis in 2014. At this point, FreeM would not compile or run on modern Linux systems, so steps were taken to remedy the most pressing issues in the codebase. Limitations on the terminal size (previously hard-coded to 80x25) were lifted, and new @code{$VIEW} functions were added to retrieve the terminal size information. @code{$X} and @code{$Y} intrinsic special variables were updated to support arbitrary terminal sizes, and FreeM was once again able to build and run.
- In February of 2020, work began in earnest to build a development and support infrastructure for FreeM and begin the careful process of refining it into a more stable and robust product.
+ In February of 2020, work began in earnest to build a development and support infrastructure for FreeM and begin the careful process of refining it into a more stable and robust application.
+ For more information on FreeM history, see @code{@emph{$PREFIX}/share/freem/doc/freem_history.*} (distributed in PostScript, PDF, and plain text formats).
  @section Production Readiness
- Line 225  Serena Willis (Current Maintainer and Pr
+ Line 229  Serena Willis (Current Maintainer and Pr
  Steve Zeck (Code)
  @end itemize
+ @node Document Conventions
+ @chapter Document Conventions
+ @cindex document conventions
+ @cindex conventions
+ @section Formatting Conventions
+ This manual uses the following formatting conventions:
+ @itemize
+ @item Code examples, filesystem paths, and commands are presented in @code{monospace}
+ @item Placeholders where the reader is expected to supply a replacement value are presented in @code{@emph{monospace italics}}, and depending on context, may be surrounded by angle brackets
+ @item New terminology is introduced in @emph{proportional italics}
+ @end itemize
+ @section Definitions
+ FreeM uses abbreviations for common language elements:
+ @table @asis
+ @item @emph{$PREFIX}
+ Refers to the base filesystem location within which FreeM is installed. For most distribution methods of FreeM, @emph{$PREFIX} represents either @code{/} or @code{/usr/local}.
+ @item @emph{dlabel}
+ Refers to a label in an M routine, beginning in the first column of the line. Can be a @emph{name} or an @emph{intlit}.
+ @item @emph{entryref}
+ Refers to an M routine entry point, denoted in the format @code{@emph{dlabel} [+@emph{intexpr}][^@emph{routine}]}.
+ @item @emph{expr}
+ Refers to any expression. Often presented in the format @emph{expr V <type>}, where @emph{V} means @emph{giving}; e.g., @emph{expr V lvn} means @emph{expression giving local variable name}.
+ @item @emph{glvn}
+ Refers to the name of an M global, local, or structured system variable.
+ @item @emph{gvn}
+ Refers to the name of an M global variable.
+ @item @emph{intexpr}
+ Refers to an integer expression.
+ @item @emph{intlit}
+ Refers to an integer literal.
+ @item @emph{ISV}, @emph{isv}
+ Refers to an M intrinsic special variable; @code{$JOB} and @code{$IO} are examples of ISVs.
+ @item @emph{L}
+ Indicates a @emph{list} of the following item, e.g., @emph{L gvn} means @emph{list of global variable names}.
+ @item @emph{lvn}
+ Refers to the name of an M local variable.
+ @item @emph{strlit}
+ Refers to an M string literal.
+ @item @emph{ssvn}
+ Refers to the name of an M structured system variable.
+ @item @emph{tvexpr}
+ Refers to a truth-valued expression.
+ @end table
+ @node A Note on Standards
+ @chapter A Note on Standards
+ @cindex MDC
+ @cindex M Development Committee
+ @cindex ANSI X11.1
+ @cindex standards, ANSI
+ @cindex standards, MDC
+ FreeM attempts to implement as many features as possible from the M Development Committee's unpublished @emph{Millennium Draft Standard}, as well as its predecessors.
+ The maintainer of FreeM (who is also the author of this book) is largely in favor of standardization efforts, and hopes that the MDC will resume activities, and will happily participate if it does so in an open, public, transparent, and democratic manner. Until then, however, FreeM will attempt to improve the M language, in cooperation with other free software M implementers where possible. Any breaking changes introduced in future MDC releases of the @emph{Standard} (such as the rumored @emph{M5}) which prove incompatible with FreeM will be handled via the @code{$DIALECT} special variable (to be changed to @code{$ZDIALECT} in a coming release).
+ The conformance document required per the @emph{Standard} should be installed as a @code{man} page on any computer system where FreeM is made available. Simply type @code{man freem_conformance} to access.
  @node FreeM Invocation
  @chapter FreeM Invocation
  @cindex invocation, command-line
- Line 241  When @code{-r} or @code{--routine} are p
+ Line 309  When @code{-r} or @code{--routine} are p
  @section %SYSINIT Routine
- The @code{%SYSINIT} routine runs every time a FreeM interpreter process starts. This routine defines some useful constants, enables handling of @code{TRIGGER} events, and handles the execution of code passed via the @code{-x\--execute} or routines passed via @code{-r|--routine}.
+ The @code{%SYSINIT} routine runs every time a FreeM interpreter process starts. This routine defines some useful constants, enables handling of @code{TRIGGER} events, and handles the execution of code passed via the @code{-x|--execute} or routines passed via @code{-r|--routine}.
  Do not modify the supplied @code{%SYSINIT} routine to add site-specific startup items. Instead, create a @code{LCLINIT} routine in the @code{USER} namespace of one or more environments. @code{%SYSINIT} will automatically run @code{LCLINIT} each time it starts.
- Line 371  Attempting to start a FreeM interpreter
+ Line 439  Attempting to start a FreeM interpreter
  The FreeM direct-mode environment is the mode entered when FreeM is invoked without the use of @option{-r @emph{<entryref>}} or @option{--routine=@emph{<entryref>}}:
  @example
- Coherent Logic Development FreeM version 0.64.0-rc0 (x86_64-pc-linux-gnu)
+ Coherent Logic Development FreeM version 0.64.0-rc1 (x86_64-pc-linux-gnu)
  Copyright (C) 2014, 2020, 2021 Coherent Logic Development LLC
- Line 523  DEFAULT.USER>
+ Line 591  DEFAULT.USER>
  Such expressions will be immediately evaluated, and the result printed on @code{@ref{$IO}}.
+ @node Debugging
+ @chapter Debugging
+ @cindex debugging
+ @section Debugging Synopsis
+ FreeM includes an interactive debugger, entered using the @code{BREAK "DEBUG"} command. The debugger is also entered if @code{Ctrl-C} is pressed, @code{Ctrl-C} handling is enabled, and you are in direct mode.
+ If you would like to enter the debugger automatically each time an error is encountered, add the following to your @code{LCLINIT} routine:
+ @example
+ S $ETR="B ""DEBUG"""
+ @end example
+ @section Debugging Commands
+ The debugger uses its own unique command language, where M commands are unavailable. Commands are as follows:
+ @table @asis
+ @item @code{exit}, @code{quit}
+ Exits the debugger and returns to direct mode or normal program execution.
+ @item @code{e} @emph{glvn}, @code{examine} @emph{glvn}
+ Prints the value of @emph{glvn} to the terminal.
+ @item @code{t}, @code{trace}
+ Toggles @emph{trace mode} on and off. When trace mode is on, FreeM will display information about each @code{DO} or @code{GOTO} command encountered, including the routine which invoked the branch, which type of branch was invoked, and the target of the branch.
+ @item @code{s}, @code{step}
+ Single-steps through FreeM code command-by-command.
+ @item @code{n}, @code{next}
+ Single-steps through FreeM code line-by-line.
+ @item @code{c}, @code{cont}, @code{continue}
+ Resumes normal program execution, disabling single-step mode.
+ @item @code{bt}, @code{backtrace}
+ Produces a stack trace.
+ @item @code{h}, @code{halt}
+ Halts the process being debugged and returns control to the operating system.
+ @item @code{w [[+|-|?]@emph{<glvn>}]}, @code{watch [[+|-|?]@emph{<glvn>}]}
+ With no arguments, toggles watchpoints on and off. With @code{+}, adds @emph{<glvn>} to the watchlist. With @code{-}, removes @emph{<glvn>} from the watchlist. With @code{?}, queries the watch status of @emph{<glvn>}.
+ @end table
  @node Directives
  @chapter Directives
  @cindex directives
- Line 593  Please note that FreeM is not entirely s
+ Line 698  Please note that FreeM is not entirely s
  * $SYSTEM::                  MDC system ID of FreeM.
  * $TEST::                    Truth value of last conditional expression or result of certain @code{LOCK} operations.
  * $TLEVEL::                  Current level of transaction nesting.
- * $WITH::                    Current variable prefix set by @code{WITH} command.
+ * $WITH::                    Current variable prefix set by @code{ZWITH} command.
  * $X::                       Current horizontal screen position.
  * $Y::                       Current vertical screen position.
  * $ZA::                      Current position of file on @code{$IO}.
- Line 789  uncommitted transactions exist.
+ Line 894  uncommitted transactions exist.
  @cindex $WITH
  @cindex intrinsic special variables, $WITH
- Returns the variable prefix set by the @code{@ref{WITH}} command.
+ Returns the variable prefix set by the @code{@ref{ZWITH}} command.
  @node $X
  @section $X
- Line 1912  Identical to @ref{$TRANSLATE()}, except
+ Line 2017  Identical to @ref{$TRANSLATE()}, except
  * AUNBLOCK::                            Decrement the block counter for one or more event classes.
  * BREAK::                               Interrupt a running routine to allow interactive debugging.
  * CLOSE::                               Close an input/output device.
- * CONST::                               Define a constant that cannot be altered after initial definition.
  * DO::                                  Transfer program control to one or more subroutines or introduces a new execution level.
  * ELSE::                                Execute the remainder of a line if @code{@ref{$TEST}} evaluates @emph{false}.
  * FOR::                                 Repeat execution of a line or block of code.
- Line 1925  Identical to @ref{$TRANSLATE()}, except
+ Line 2029  Identical to @ref{$TRANSLATE()}, except
  * KSUBSCRIPTS::                         Kill only the descendant subscripts of a local, global, global, or structured system variable.
  * KVALUE::                              Kill only the value of a local, global, or structured system variable.
  * LOCK::                                Control advisory locking for concurrency control.
- * MAP::                                 Map a global name to a non-default namespace.
  * MERGE::                               Merge contents of one local, global, or structured system variable into another.
  * NEW::                                 Introduce a new scope for a specified local variable or intrinsic special variable or instantiate an object.
  * OPEN::                                Open a sequential or socket input/output device.
- Line 1934  Identical to @ref{$TRANSLATE()}, except
+ Line 2037  Identical to @ref{$TRANSLATE()}, except
  * SET::                                 Set the value of a local variable, global, intrinsic special variable, or structured system variable.
  * TCOMMIT::                             Commit a transaction.
  * THEN::                                Preserve @code{@ref{$TEST}} until the end of the current line.
- * THROW::                               Programmatically raise an error condition.
  * TROLLBACK::                           Roll back all pending transactions.
  * TSTART::                              Introduce a new transaction processing level.
- * UNMAP::                               Remove a mapping of a global to a non-default namespace.
  * USE::                                 Set the currently-active input/output device.
  * VIEW::                                Modify FreeM internal parameters.
- * WATCH::                               Enable or disable watchpoints, or set or clear watchpoints on specified globals, locals, or structured system variables.
- * WITH::                                Set prefix for future variable references.
  * WRITE::                               Write output to current input/output device.
  * XECUTE::                              Interpret string as M code.
  * ZBREAK::                              Unknown.
+ * ZCONST::                              Define a constant that cannot be altered after initial definition.
  * ZGO::                                 Unknown.
  * ZHALT::                               Unknown.
  * ZINSERT::                             Insert code into routine buffer.
- * ZJOB::                                Unknown.
+ * ZJOB::                                Invokes a job, ignoring any timeouts.
  * ZLOAD::                               Load routine into routine buffer.
+ * ZMAP::                                Map a global name to a non-default namespace.
  * ZNEW::                                Unknown.
  * ZPRINT::                              Print contents of routine buffer.
- * ZQUIT::                               Unknown.
+ * ZQUIT::                               Quits multiple stack levels at once.
  * ZREMOVE::                             Remove code from routine buffer.
  * ZSAVE::                               Save routine buffer to disk.
+ * ZTHROW::                              Programmatically raise an error condition.
  * ZTRAP::                               Unknown.
+ * ZUNMAP::                              Remove a mapping of a global to a non-default namespace.
+ * ZWATCH::                              Enable or disable watchpoints, or set or clear watchpoints on specified globals, locals, or structured system variables.
+ * ZWITH::                               Set prefix for future variable references.
  * ZWRITE::                              Write local variable, global, or structured system variable to @code{@ref{$IO}}.
  @end menu
- Line 2216  In its argumentless form, @code{BREAK} s
+ Line 2321  In its argumentless form, @code{BREAK} s
  @emph{FreeM Extension}
- In its single-argument form, @code{BREAK} sets @emph{Ctrl-C} handling and error handling characteristics, provided the optional @emph{postcondition} is @emph{true} or omitted.
+ In its single-argument form, @code{BREAK} enters the interactive debugger or sets @emph{Ctrl-C} handling and error handling characteristics, provided the optional @emph{postcondition} is @emph{true} or omitted.
  The following table enumerates the possible values of @emph{breakflag}
  @table @code
+ @item "DEBUG"
+ Enters the interactive debugger
  @item 0
  Disables @emph{Ctrl-C} handling
  @item -2
- Line 2251  In its argumentless form, @code{CLOSE} c
+ Line 2358  In its argumentless form, @code{CLOSE} c
  In its single-argument form, @code{CLOSE} closes the I/O device associated with channel @emph{channel}, provided that @emph{channel} represents a currently-open device, and the optional @emph{postcondition} is @emph{true} or omitted.
- @node CONST
- @section CONST
- @cindex CONST
- @cindex commands, CONST
- @cindex commands, non-standard
- @emph{FreeM Extension}
- Defines a local @emph{constant}, or variable that cannot be altered after its initial definition, provided the optional @emph{postcondition} is @emph{true} or omitted.
- Constants must only be locals, and globals are not supported.
- @emph{Syntax}
- @example
- @code{CONST@emph{:postcondition} @emph{mref1}=@emph{initial-value1},...,@emph{mrefN}=@emph{initial-valueN}}
- @end example
  @node DO
  @section DO
  @cindex DO
- Line 2281  In its inclusive form, transfers program
+ Line 2371  In its inclusive form, transfers program
  DO[@emph{:postcondition}] @emph{entryref}[@emph{:postcondition}[,...]]
  @end example
+ @cartouche
+ @quotation
+ @emph{Non-Standard Behavior}
+ FreeM allows @code{DO} @emph{entryref}s to follow the format of @code{+@emph{intexpr}}. In this case, the value of @emph{intexpr} will be interpreted as an offset from the first line of the current routine.
+ @end quotation
+ @end cartouche
  In its argumentless form, transfers control to the following block of code where the line level is one greater than the level at which @code{DO} was encountered, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
  @emph{Syntax}
- Line 2306  ELSE[@emph{:postcondition}]
+ Line 2404  ELSE[@emph{:postcondition}]
  @quotation
  @emph{Non-Standard Behavior}
- FreeM allows a @emph{postcondition} on @code{ELSE}. While explicitly forbidden in the @emph{standard}--and for good reason--it was decided that FreeM should allow postconditions everywhere, both for the sake of foolish consistency (the likes of which Emerson warned against), and for the benefit of entrants to a hypothetical future obfuscated M contest, and those with a Machiavellian predisposition to wicked perversions and undue cleverness.
+ FreeM allows a @emph{postcondition} on @code{ELSE}. While explicitly forbidden in the @emph{Standard}, it was decided that FreeM should allow postconditions everywhere, both for the sake of foolish consistency (the likes of which Emerson warned against), and for the benefit of entrants to a hypothetical future obfuscated M contest, and those with a Machiavellian predisposition to wicked perversions and undue cleverness.
- Using postconditions on @code{ELSE} should be strictly avoided in production code, as they have no practical use, and may contribute to technical debt, hardening of the arteries, hobgoblins, a small mind, a surfeit of logic, climate change, Daily WTF rants, or meltdown of global financial markets.
+ Using postconditions on @code{ELSE} should be strictly avoided in production code, as they have no practical use, and may contribute to technical debt, hardening of the arteries, hobgoblins, a small mind, a surfeit of logic, climate change, @emph{Daily WTF} rants, or the meltdown of global financial markets.
  @end quotation
  @end cartouche
- Line 2404  Transfers program execution to another l
+ Line 2502  Transfers program execution to another l
  GOTO[@emph{:postcondition}] @emph{entryref}
  @end example
+ @cartouche
+ @quotation
+ @emph{Non-Standard Behavior}
+ FreeM allows @code{GOTO} @emph{entryref}s to follow the format of @code{+@emph{intexpr}}. In this case, the value of @emph{intexpr} will be interpreted as an offset from the first line of the current routine.
+ @end quotation
+ @end cartouche
  @node HALT
  @section HALT
  @cindex HALT
- Line 2452  IF[@emph{:postcondition}] @emph{tvexpr}[
+ Line 2559  IF[@emph{:postcondition}] @emph{tvexpr}[
  In its argumentless form, allows the remainder of the line of code following @code{IF} to execute only if @code{$TEST} evaluates to @emph{1}, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
  @emph{Syntax}
  @example
- IF[@emph{:postcondition}]
+ IF[@emph{:postcondition}]  @emph{command...}
  @end example
+ @cartouche
+ @quotation
+ @emph{Style Recommendation}
+ In the interest of readability and maintainability, we recommend avoiding the argumentless form of @code{IF} in new code. It is an obsolete relic of an era when routine sizes were severely limited, and can be difficult to spot, as the use of whitespace (@code{IF  @emph{command}}) makes the intent of its use non-obvious at a glance. It is also far too easy to inadvertently delete the extra space, leading to program errors easily avoided otherwise.
+ We recommend explicitly checking the value of @code{$TEST} instead, as in @code{IF $TEST @emph{command}} or @code{@emph{command}:$TEST ...}, as this makes the intent immediately clear both to M newcomers and seasoned experts, and sacrifices nothing of value, even on the oldest computer systems where FreeM can be used today.
+ @end quotation
+ @end cartouche
  @node JOB
  @section JOB
  @cindex JOB
- Line 2515  In the above @emph{inclusive} form, @cod
+ Line 2633  In the above @emph{inclusive} form, @cod
  @cartouche
  @quotation
  @emph{Note}
- The below @emph{argumentless} and @emph{exclusive} forms of @code{KSUBSCRIPTS} are not implemented in FreeM, as of version 0.64.0-rc0, but are planned for a future release.
+ The below @emph{argumentless} and @emph{exclusive} forms of @code{KSUBSCRIPTS} are not implemented in FreeM, as of version 0.64.0-rc1, but are planned for a future release.
  @end quotation
  @end cartouche
- Line 2550  In the above @emph{inclusive} form, @cod
+ Line 2668  In the above @emph{inclusive} form, @cod
  @cartouche
  @quotation
  @emph{Note}
- The below @emph{argumentless} and @emph{exclusive} forms of @code{KVALUE} are not implemented in FreeM, as of version 0.64.0-rc0, but are planned for a future release.
+ The below @emph{argumentless} and @emph{exclusive} forms of @code{KVALUE} are not implemented in FreeM, as of version 0.64.0-rc1, but are planned for a future release.
  @end quotation
  @end cartouche
- Line 2606  If @code{LOCK} succeeds within @emph{tim
+ Line 2724  If @code{LOCK} succeeds within @emph{tim
  LOCK[@emph{:postcondition}] @emph{name}[:@emph{timeout}][,...@emph{name}[:@emph{timeout}]]
  @end example
- @node MAP
- @section MAP
- @cindex MAP
- @cindex commands, MAP
- @cindex commands, implementation-specific
- @cindex commands, non-standard
- Maps global name @code{gvn} to be mapped to the non-default namespace @emph{expr V namespace}, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
- @emph{Syntax}
- @example
- MAP[@emph{:postcondition}] GLOBAL @emph{gvn}=@emph{expr V namespace}
- @end example
  @node MERGE
  @section MERGE
  @cindex MERGE
- Line 2870  Saves the value of @code{$TEST} until th
+ Line 2973  Saves the value of @code{$TEST} until th
  IF 1 THEN  WRITE "HELLO!",!
  @end example
- @node THROW
- @section THROW
- @cindex THROW
- @cindex commands, THROW
- @cindex commands, non-standard
- @emph{FreeM Extension}
- Raises an error condition as long as the optional @emph{postcondition} is @emph{true} or omitted.
- @emph{Syntax}
- @example
- @code{THROW@emph{:postcondition} @emph{expr V error-code}}
- @end example
- @emph{Example}
- @example
- @code{THROW "M102"}
- @end example
  @node TROLLBACK
  @section TROLLBACK
  @cindex TROLLBACK
- Line 2955  If you are using more than one transacti
+ Line 3037  If you are using more than one transacti
  TSTART (FOO,BAR):(SERIAL,TRANSACTIONID="FOO")
  @end example
- @node UNMAP
- @section UNMAP
- @cindex UNMAP
- @cindex commands, UNMAP
- @cindex commands, implementation-specific
- @cindex commands, non-standard
- Removes any mapping connecting @emph{gvn} to a non-default namespace, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
- @emph{Syntax}
- @example
- UNMAP GLOBAL @emph{gvn}
- @end example
  @node USE
  @section USE
- Line 3273  VIEW 133:@emph{tvexpr}
+ Line 3341  VIEW 133:@emph{tvexpr}
  @end table
- @node WATCH
- @section WATCH
- @cindex WATCH
- @cindex commands, WATCH
- @cindex commands, debugging
- @cindex commands, implementation-specific
- @cindex commands, non-standard
- @emph{FreeM Extension}
- Sets a watchpoint on a global, local, or SSVN node.
- @emph{Syntax}
- In its @emph{argumentless} form, @code{WATCH} toggles watchpoints on and off, provided the optional @emph{postcondition} is @emph{true} or omitted.
- @example
- WATCH[@emph{:postcondition}]
- @end example
- In its @emph{inclusive} form, @code{WATCH} adds, removes, or examines watchpoints, provided the optional @emph{postcondition} is @emph{true} or omitted.
- A @code{+} adds a new watchpoint to the following variable.
- A @code{-} removes an existing watchpoint for the following variable.
- A @code{?} examines the status of a watchpoint for the following variable.
- @example
- WATCH[@emph{:postcondition}] [+|-|?]@emph{var1}...,[+|-|?]@emph{varN}
- @end example
- The following example demonstrates turning watchpoint processing on and adding a watchpoint for global variable @code{^snw(1)}. It then changes the value of @code{^snw(1)}.
- @example
- DEFAULT.USER> WATCH
- Watchpoints enabled.
- DEFAULT.USER> WATCH +^SNW(1)
- Added '^SNW("1")' to the watchlist.
- DEFAULT.USER> SET ^SNW(1)="new value"
- >> WATCHPOINT:  ^SNW("1") => 'new value' (changed 1 times)
- @end example
- The following example will remove that watchpoint:
- @example
- DEFAULT.USER> WATCH -^SNW(1)
- Removed '^SNW("1")' from the watchlist.
- DEFAULT.USER> WATCH ?^SNW(1)
- '^SNW("1")' is not being watched.
- @end example
- @node WITH
- @section WITH
- @cindex WITH
- @cindex commands, WITH
- @cindex commands, non-standard
- @emph{FreeM Extension}
- NOTE: This command may be deprecated and removed in future FreeM releases.
- Sets a prefix to be applied to all subsequent local variable or constant references.
- @emph{Syntax}
- @example
- @code{WITH@emph{:postcondition} @emph{var-prefix}}
- @end example
- In the above single-argument form, sets the @code{$WITH} prefix to @emph{var-prefix}, provided that the optional @emph{postcondition} is either @emph{true} or omitted.
- The @emph{var-prefix} argument may be a string literal or any valid FreeM expression.
- @example
- @code{WITH@emph{:postcondition}}
- @end example
- In the above argumentless form, clears the @code{$WITH} prefix, provided the optional @emph{postcondition} is either @emph{true} or omitted. Equivalent to @code{WITH ""}.
  @node WRITE
- Line 3382  In the above argumentless form, clears t
+ Line 3362  In the above argumentless form, clears t
  @cindex commands, non-standard
  @emph{FreeM Extension}
+ @node ZCONST
+ @section ZCONST
+ @cindex ZCONST
+ @cindex commands, ZCONST
+ @cindex commands, non-standard
+ @emph{FreeM Extension}
+ Defines a local @emph{constant}, or variable that cannot be altered after its initial definition, provided the optional @emph{postcondition} is @emph{true} or omitted.
+ Constants must only be locals, and globals are not supported.
+ @emph{Syntax}
+ @example
+ @code{ZCONST@emph{:postcondition} @emph{mref1}=@emph{initial-value1},...,@emph{mrefN}=@emph{initial-valueN}}
+ @end example
  @node ZGO
  @section ZGO
  @cindex ZGO
- Line 3434  Loads routine @emph{<routine-name>} into
+ Line 3431  Loads routine @emph{<routine-name>} into
  ZLOAD@emph{:postcondition} @emph{<routine-name>}
  @end example
+ @node ZMAP
+ @section ZMAP
+ @cindex ZMAP
+ @cindex commands, ZMAP
+ @cindex commands, implementation-specific
+ @cindex commands, non-standard
+ Maps global name @code{gvn} to be mapped to the non-default namespace @emph{expr V namespace}, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
+ @emph{Syntax}
+ @example
+ ZMAP[@emph{:postcondition}] GLOBAL @emph{gvn}=@emph{expr V namespace}
+ @end example
  @node ZNEW
  @section ZNEW
  @cindex ZNEW
- Line 3492  In its argumentless form, quits from @co
+ Line 3505  In its argumentless form, quits from @co
  @cindex commands, non-standard
  @emph{FreeM Extension}
+ @node ZTHROW
+ @section ZTHROW
+ @cindex ZTHROW
+ @cindex commands, ZTHROW
+ @cindex commands, non-standard
+ @emph{FreeM Extension}
+ Raises an error condition as long as the optional @emph{postcondition} is @emph{true} or omitted.
+ @emph{Syntax}
+ @example
+ @code{ZTHROW@emph{:postcondition} @emph{expr V error-code}}
+ @end example
+ @emph{Example}
+ @example
+ @code{ZTHROW "M102"}
+ @end example
  @node ZTRAP
  @section ZTRAP
  @cindex ZTRAP
- Line 3501  In its argumentless form, quits from @co
+ Line 3536  In its argumentless form, quits from @co
  @cindex commands, non-standard
  @emph{FreeM Extension}
+ @node ZUNMAP
+ @section ZUNMAP
+ @cindex ZUNMAP
+ @cindex commands, ZUNMAP
+ @cindex commands, implementation-specific
+ @cindex commands, non-standard
+ Removes any mapping connecting @emph{gvn} to a non-default namespace, provided the optional @emph{postcondition} evaluates to @emph{true} or is omitted.
+ @emph{Syntax}
+ @example
+ ZUNMAP GLOBAL @emph{gvn}
+ @end example
+ @node ZWATCH
+ @section ZWATCH
+ @cindex ZWATCH
+ @cindex commands, ZWATCH
+ @cindex commands, debugging
+ @cindex commands, implementation-specific
+ @cindex commands, non-standard
+ @emph{FreeM Extension}
+ Sets a watchpoint on a global, local, or SSVN node.
+ @emph{Syntax}
+ In its @emph{argumentless} form, @code{ZWATCH} toggles watchpoints on and off, provided the optional @emph{postcondition} is @emph{true} or omitted.
+ @example
+ ZWATCH[@emph{:postcondition}]
+ @end example
+ In its @emph{inclusive} form, @code{ZWATCH} adds, removes, or examines watchpoints, provided the optional @emph{postcondition} is @emph{true} or omitted.
+ A @code{+} adds a new watchpoint to the following variable.
+ A @code{-} removes an existing watchpoint for the following variable.
+ A @code{?} examines the status of a watchpoint for the following variable.
+ @example
+ ZWATCH[@emph{:postcondition}] [+|-|?]@emph{var1}...,[+|-|?]@emph{varN}
+ @end example
+ The following example demonstrates turning watchpoint processing on and adding a watchpoint for global variable @code{^snw(1)}. It then changes the value of @code{^snw(1)}.
+ @example
+ DEFAULT.USER> ZWATCH
+ Watchpoints enabled.
+ DEFAULT.USER> ZWATCH +^SNW(1)
+ Added '^SNW("1")' to the watchlist.
+ DEFAULT.USER> SET ^SNW(1)="new value"
+ >> WATCHPOINT:  ^SNW("1") => 'new value' (changed 1 times)
+ @end example
+ The following example will remove that watchpoint:
+ @example
+ DEFAULT.USER> ZWATCH -^SNW(1)
+ Removed '^SNW("1")' from the watchlist.
+ DEFAULT.USER> ZWATCH ?^SNW(1)
+ '^SNW("1")' is not being watched.
+ @end example
+ @node ZWITH
+ @section ZWITH
+ @cindex ZWITH
+ @cindex commands, ZWITH
+ @cindex commands, non-standard
+ @emph{FreeM Extension}
+ NOTE: This command may be deprecated and removed in future FreeM releases.
+ Sets a prefix to be applied to all subsequent local variable or constant references.
+ @emph{Syntax}
+ @example
+ @code{ZWITH@emph{:postcondition} @emph{var-prefix}}
+ @end example
+ In the above single-argument form, sets the @code{$WITH} prefix to @emph{var-prefix}, provided that the optional @emph{postcondition} is either @emph{true} or omitted.
+ The @emph{var-prefix} argument may be a string literal or any valid FreeM expression.
+ @example
+ @code{ZWITH@emph{:postcondition}}
+ @end example
+ In the above argumentless form, clears the @code{$WITH} prefix, provided the optional @emph{postcondition} is either @emph{true} or omitted. Equivalent to @code{ZWITH ""}.
  @node ZWRITE
  @section ZWRITE
  @cindex ZWRITE
- Line 4405  An @code{INTEGER} is an interpretation o
+ Line 4551  An @code{INTEGER} is an interpretation o
  @cindex data types, REAL
  @cindex types, REAL
+ A @code{REAL} is a numeric interpretation of data including a fractional part.
  @node STRING
  @section STRING
  @cindex data types, STRING
  @cindex types, STRING
+ The @code{STRING} is the fundamental FreeM data type. Other types are inferred from the context of their usage.
+ @subsection String Rules
+ The following rules apply to all FreeM strings:
+ @itemize
+ @item Must not exceed 255 characters
+ @item Must not contain @code{$C(0)}, @code{$C(201)}, or @code{$C(202)}
+ @end itemize
+ @subsection String Quoting Rules
+ Strings in FreeM must be surrounded in double quotes:
+ @example
+ SET MYSTRING="This is a string literal"
+ @end example
+ If you want to include double quotes inside of a string, simply double them:
+ @example
+ SET MYSTRING="This is a ""string literal"" with embedded double quotes"
+ @end example
  @node Custom Types (Classes)
  @section Custom Types (Classes)
  @cindex data types, custom
  @cindex types, custom
  @cindex classes
- See @ref{Classes}.
+ See @ref{Object-Oriented Programming}.
  @node Globals
  @chapter Globals
- Line 4424  See @ref{Classes}.
+ Line 4597  See @ref{Classes}.
  @cindex variables, global
  @cindex data
+ @menu
+ * Globals Overview::            Basics of FreeM persistent storage.
+ * Creating Globals::            How to create globals.
+ * Removing Globals::            How to remove globals.
+ * Global Storage::              How globals are stored.
+ @end menu
+ @node Globals Overview
+ @section Globals Overview
+ FreeM supports typical M globals, which are often described as persistent, hierachical sparse arrays. Globals make it relatively simple to include persistent data in an application without requiring the developer to use an external database management system, and offer syntax and semantics so similar to M local variables and structured system variables that moving from one to the other is seamless.
+ Each global comprises three elements:
+ @itemize @bullet
+ @item
+ An alphabetic name beginning with a caret (@code{^}) or a caret and a percent sign (@code{^%})
+ @item
+ Optionally, one or more comma-delimited subscripts, enclosed in parentheses
+ @item
+ A value of up to 255 characters in length
+ @end itemize
+ A leading percent sign in the global name will force the named global into the @code{SYSTEM} namespace of the current FreeM environment.
+ @node Creating Globals
+ @section Creating Globals
+ @cindex globals, creating
+ To create a global, you can use the @code{SET} command:
+ @example
+ SET ^MYGLOBAL("foo","bar")="this is the data value"
+ @end example
+ @node Removing Globals
+ @section Removing Globals
+ @cindex globals, removing
+ To remove an entire global, you can use the @code{KILL} command with the unsubscripted name of the global:
+ @example
+ KILL ^MYGLOBAL
+ @end example
+ If you only want to remove part of a global, i.e., beginning at a certain subscript level, use the @code{KILL} command with a subscripted name:
+ @example
+ KILL ^MYGLOBAL("foo")
+ @end example
+ This will remove only the @code{"foo"} subscript and all of its children.
+ If you only want to remove the data value at a specific subscript level, leaving the subscript itself intact, use @code{KVALUE}:
+ @example
+ KVALUE ^MYGLOBAL("foo")
+ @end example
+ @node Global Storage
+ @section Global Storage
+ @cindex globals, storage
+ FreeM globals are stored in @code{$PREFIX/var/freem/@emph{<environment-name>}/@emph{<namespace-name>}/globals} in a binary format.
+ Global files have a header of the following format:
+ @verbatim
+ typedef struct global_header {
+     char magic[5]; /* FRMGL */
+     int format_version;
+     char host_triplet[40];
+     char host_id[256];
+     unsigned long block_size;
+     unsigned long last_transaction_id;
+     long created;
+     long last_backup;
+ } global_header;
+ @end verbatim
  @node Concurrency Control
  @chapter Concurrency Control
  @cindex concurrency control
  @cindex locking
  @cindex transaction processing
+ @menu
+ * Concurrency Control Overview::                Basics of concurrency control.
+ * Advisory Locks::                              Coordinating access voluntarily.
+ * Transaction Processing::                      Ensuring logical consistency.
+ @end menu
+ @node Concurrency Control Overview
+ @section Concurrency Control Overview
+ Multitasking, multi-user FreeM applications must concern themselves with conscientious management of concurrent access to globals in order to maintain logical consistency and prevent concurrent reads and writes from conflicting with each other.
+ In FreeM, there are two mechanisms provided for managing concurrent global access: @emph{advisory locks}, and @emph{transaction processing}.
+ Advisory locks allow applications to voluntarily coordinate concurrent access to globals with the @code{LOCK} command, and require each application to check the @code{LOCK} status prior to accessing a global.
+ Transaction processing allows applications to delineate sets of global operations (sets, kills, etc.) as being part of a transaction, in which no operations are performed against the globals contained within the transaction until the transaction is committed. In addition, processes other than the one running the transaction will be forced to wait to access globals for either the duration of the commit phase (@emph{batch mode}), or for the entire duration of the transaction (@emph{serial mode}).
+ @node Advisory Locks
+ @section Advisory Locks
+ @node Transaction Processing
+ @section Transaction Processing
+ @cindex transaction processing
+ FreeM implements a significant subset of the transaction processing features from @emph{ANSI X11.1-1995}. This allows a series of global operations to be conducted all at once, either in batch mode (where concurrent operation is not interrupted until the last possible moment), or in serial mode (where writes are guaranteed to be atomic, consistent, isolated, and durable).
+ @subsection Theory of Operation
+ FreeM uses a pessimistic concurrency control mechanism for @code{SERIAL} transactions, meaning that any @code{TSTART} command that includes the @code{SERIAL} transaction parameter will cause the process to acquire the transaction processing mutex, which prevents any process but the one holding the mutex from performing any data access (read or write) until either @code{TCOMMIT} or @code{TROLLBACK} is called, either committing or rolling back the transaction, respectively.
+ Any transaction in between its @code{TSTART} and @code{TCOMMIT}/@code{TROLLBACK} is said to be @emph{in-flight}. During the in-flight stage, pending global operations are held only in memory and after-image journals.
+ FreeM maintains a list of all globals affected during a transaction in-flight. When a @code{TCOMMIT} is reached, FreeM will generate a @emph{checkpoint} of each global data file to be changed by the transaction. These checkpoints allow all FreeM globals to be restored to their pre-transaction state if a @code{TCOMMIT} should fail part of the way through its operation.
+ Checkpoints can have one of two modes:
+ @table @asis
+ @item @code{CP_REMOVE}
+ Used for globals that did not exist prior to the beginning of this transaction. Simply marks the entire global data file for deletion in case of @code{TCOMMIT} failure.
+ @item @code{CP_RESTORE}
+ Used for globals that @emph{did} exist prior to the beginning of this transaction. In this case, the entire global data file is copied to a new file with a @code{.chk} extension. In cases of @code{TCOMMIT} failure, @code{CP_RESTORE} checkpoint files will be restored over the partially-modified live data file.
+ @end table
+ The below example shows a few global operations and checkpoints for a transaction in-flight using the @code{trantab} direct-mode command:
+ @verbatim
+ TL1:DEFAULT.USER> trantab
+  $TLEVEL 1*
+   Operations for Transaction ID: 6ea14aad-b8f1-47f9-9f52-4f513f892bc0 [RESTARTABLE SERIAL]
+    OP. NO.   ACTION         KEY/DATA
+    -------   ------         --------
+        SET            ^FOO=3
+        KILL           ^FOO
+        SET            ^snw=10
+        SET            ^BRANDNEW=6
+   Global checkpoints:
+    GLOBAL                        MODE                FILES
+    ------                        ----                -----
+    ^BRANDNEW                     CP_REMOVE           IN:   /usr/local/var/freem/USER/globals/^BRANDNEW
+    ^snw                          CP_RESTORE          IN:   /usr/local/var/freem/USER/globals/^snw
+                                                      OUT:  /usr/local/var/freem/USER/globals/^snw.23390.1.chk
+    ^FOO                          CP_RESTORE          IN:   /usr/local/var/freem/USER/globals/^FOO
+                                                      OUT:  /usr/local/var/freem/USER/globals/^FOO.23390.1.chk
+ @end verbatim
+ In the above example, @code{IN} files are the live data file that will be overwritten or removed, and @code{OUT} files are the checkpoints themselves. Note that @code{OUT} files are only used for @code{CP_RESTORE} checkpoints.
+ @subsection Using Transaction Processing
+ To use transactions in FreeM, you need to be familiar with three commands:
+ @itemize @bullet
+ @item
+ @code{TSTART}
+ @item
+ @code{TCOMMIT}
+ @item
+ @code{TROLLBACK}
+ @end itemize
+ With transaction processing, global variable operations occurring between @code{TSTART} and @code{TCOMMIT} commands will be contained within the transaction.
+ The atomicity, consistency, isolation, and durability facets of FreeM transaction hinge on the transaction mode.
+ @subsubsection BATCH Transactions
+ @code{BATCH} transactions offer higher performance, and allow other applications aside from the one doing the transaction to continue normal operations until the transaction is committed with @code{TCOMMIT}. In batch mode, other processes are only locked out of normal operation during the commit phase of the transaction.
+ The effect of this is that the operations within the batch transaction will not be interleaved with global writes from other applications, but the entire lifetime of the transaction is not guaranteed to be serialized with respect to the transaction processing activities of other running applications in the environment.
+ @subsubsection SERIAL Transactions
+ @code{SERIAL} transactions offer full ACID compliance at the expense of multiprocessing performance. In serial mode, a @code{TSTART} blocks all activity from all other FreeM processes in the environment, and this blocking effect is not released until the transaction is committed with @code{TCOMMIT} or rolled back with @code{TROLLBACK} (or due to abnormal conditions in the environment that preclude the successful completion of the transaction).
  @node Local Variables
  @chapter Local Variables
  @cindex variables, local
  @cindex local variables
+ @menu
+ * Local Variables Overview::            The basics of locals.
+ * Creating Local Variables::            Creating locals with SET.
+ * Removing Local Variables::            Removing locals with KILL.
+ @end menu
+ @node Local Variables Overview
+ @section Local Variables Overview
+ FreeM @emph{local variables} have the same data structure as global variables, but are scoped to a single FreeM process, and stored in memory.
+ Each local comprises three elements:
+ @itemize @bullet
+ @item
+ An alphabetic name beginning with a letter or a percent sign (@code{%})
+ @item
+ Optionally, one or more comma-delimited subscripts, enclosed in parentheses
+ @item
+ A value of up to 255 characters in length
+ @end itemize
+ @node Creating Local Variables
+ @section Creating Local Variables
+ @cindex local variables, creating
+ To create a local variable, use the @code{SET} command:
+ @example
+ SET MYLOCAL("foo","bar")="this is the data value"
+ @end example
+ @node Removing Local Variables
+ @section Removing Local Variables
+ @cindex local variables, removing
+ To remove an entire local variable, you can use the @code{KILL} command with the unsubscripted name of the variable:
+ @example
+ KILL MYLOCAL
+ @end example
+ If you only want to remove part of a local variable, i.e., beginning at a certain subscript level, use the @code{KILL} command with a subscripted name:
+ @example
+ KILL MYLOCAL("foo")
+ @end example
+ This will remove only the @code{"foo"} subscript and all of its children.
+ If you only want to remove the data value at a specific subscript level, leaving the subscript itself intact, use @code{KVALUE}:
+ @example
+ KVALUE MYLOCAL("foo")
+ @end example
  @node Scoping
  @chapter Scoping
  @cindex scoping
+ By default, FreeM local variables and their values are scoped to the entire process, meaning that any function or subroutine can access and modify their values. This can lead to pernicious bugs.
+ M provides the @code{NEW} command to work around these issues. When @code{NEW} is called with a local variable as its argument, FreeM will scope the variable to the process stack frame in which the @code{NEW} command occured. When exiting the stack frame (i.e. with the @code{QUIT} command), FreeM will restore the variable to its value prior to being @code{NEW}ed.
+ @emph{Example}
+ @example
+ MYRTN ;
+   S J=1 ; set local variable J to 1
+   W J,! ; this will output "1"
+   D X   ; execute subroutine X
+   W J,! ; this will output "1", as the value of J was restored
+   Q
+   ;;
+ X ;
+   N J   ; stack J
+   S J=6 ; set its value to 6
+   W J,! ; this will output "6"
+   Q     ; quit from the subroutine, destroying its stack frame
+   ;;
+ @end example
+ @section Scoping Considerations for $TEST
+ In M, the truth value of comparisons, logic operations, and certain forms of @code{LOCK} is stored in the @code{$TEST} intrinsic special variable, which follows the same rules as any M local variable.
+ This is probably the most significant design flaw of the language, as the side effects of logic on @code{$TEST} lead to incredibly difficult bugs. However, M allows @code{$TEST} to be @code{NEW}ed, and FreeM provides the @code{THEN} command@footnote{From MDC Type A extension X11/1998-31} to help in the case of conditionals. @code{THEN} stacks @code{$TEST} to the end of the line.
+ When writing new M code in FreeM, we strongly suggest using @code{THEN} as follows:
+ @example
+ MYRTN ;
+   IF MYVAR=1 THEN DO SUBRT
+ @end example
+ This is instead of the traditional form:
+ @example
+ MYRTN ;
+   IF MYVAR=1 DO SUBR
+ @end example
+ @cartouche
+ @quotation
+ @emph{Style Recommendation}
+ Note that @code{THEN} is not in any currently published version of the @emph{Standard}, but is part of MDC Type A extension X11/1998-31. However, we recommend using @code{THEN} instead of favoring portability, as there is no defensible reason for this incredibly simple feature @emph{not} to be ubiquitous.
+ If you use other M implementations, you should bug the implementers to implement @code{THEN}, as it at least partially mitigates an inexcusable flaw in the design of M.
+ @end quotation
+ @end cartouche
  @node Decision Constructs
  @chapter Decision Constructs
  @cindex decision constructs
- Line 4482  See @ref{Classes}.
+ Line 4945  See @ref{Classes}.
  @cindex programming, object-oriented
  @menu
- * Classes::             The basis of object-oriented programming.
+ * Classes::                             The organizing concept of object-oriented programming.
+ * Inheritance::                         Making one class derive from another.
+ * Methods::                             Attach code to classes.
+ * Public and Private Variables::        Determining accessibility.
+ * Instantiating Objects::               Creating instances of classes.
  @end menu
  @node Classes
  @section Classes
+ @subsection Class Overview
- @menu
+ A @emph{class} is the primary organizing concept of FreeM support for object-oriented programming, and in FreeM, is simply an M routine with a few special properties:
- * Inheritance::         Basing one class upon another.
- * Methods::             Attaching code to a class.
+ @example
- * Public Variables::    Variables visible outside of a class.
+ MYCLASS(THIS,INIT):OBJECT ; Constructor for MYCLASS, inherits OBJECT
- * Private Variables::   Variables only visible within a class.
+   ; two private variables
- @end menu
+   S THIS("NUMERATOR"):PRIVATE=$P(INIT,"/",1)
+   S THIS("DENOMINATOR"):PRIVATE=$P(INIT,"/",2)
+   Q
+   ;
+ DESTROY(THIS) ; This is the destructor
+   Q
+ @end example
+ The above example demonstrates general class syntax.
+ @subsection Constructors
+ A @emph{constructor} is an M entry point that is called when a new instance of a class is created.
+ A constructor must be the first entry point in a class routine, its tag must match the class/routine name, and it must take two arguments, @code{THIS} and @code{INIT}.
+ @code{THIS} represents the instance of the object being accessed, and @code{INIT} represents an initializer that can be used to assign an initial value to the object when instantiating the class.
+ A constructor looks like this:
+ @example
+ %FRACTION(THIS,INIT):OBJECT ;
+    S THIS("NUMERATOR"):PRIVATE=$P(INIT,"/",1)
+    S THIS("DENOMINATOR"):PRIVATE=$P(INIT,"/",2)
+    Q
+ @end example
+ @emph{Syntax}
+ @example
+ @emph{<class-name>}(THIS,INIT)[:@emph{<superclass>}]
+ @end example
+ In the above example, @emph{<superclass>} represents the name of a class from which this class should inherit. In this case, the @code{FRACTION} class inherits from the @code{OBJECT} class. Note that this is not strictly necessary in this case, as all classes in FreeM automatically inherit from @code{OBJECT}.
+ @subsection Destructors
+ A @code{destructor} is called when you @code{KILL} an instance variable. Its tag must be @code{DESTROY}, and it must take one argument (@code{THIS}).
+ The destructor should be used to clean up any resources used by class methods.
+ A destructor looks like this:
+ @example
+ DESTROY(THIS) ;
+   ; free any resources that should be freed at the end of the object's lifetime
+   Q
+ @end example
  @node Inheritance
- @subsection Inheritance
+ @section Inheritance
+ Every class you create will automatically inherit the methods and functionality of the @code{OBJECT} class, supplied with FreeM.
+ When attempting to call a method, FreeM will first search the class routine for a matching entry point, and then follow the inheritance chain upwards until a matching entry point is found. If the final class in the chain does not have a matching entry point, FreeM will try to find a matching entry point in the @code{OBJECT} class.
+ Inheritance is achieved by specifying the name of the superclass in the constructor:
+ @example
+ CLASS(THIS,INIT):SUPERCLASS
+ @end example
+ @subsection Runtime Polymorphism
+ You can achieve runtime polymorphism by subclassing, and defining methods in the subclass that match the names of existing methods in the superclass. Following FreeM inheritance rules, the overridden method in the subclass will be called, and the method in the superclass will not.
+ Note that the overridden method in the subclass can take a different set or number of arguments than the @emph{formallist} of the superclass method would specify.
  @node Methods
- @subsection Methods
+ @section Methods
+ Class methods are defined as tags with @emph{formallist}s in a class routine, and per the typical FreeM object pattern, must take at least one argument, being @code{THIS} (representing a reference to the object instance being accessed).
+ The following class (@code{MYCLASS}) has a constructor, a destructor, and a method called @code{MYMETHOD}:
+ @example
+ %MYCLASS(THIS,INIT) ;
+   Q THIS
+ DESTROY(THIS) ;
+   Q
+ MYMETHOD(THIS) ;
+   Q "VALUE"
+ @end example
+ The dot operator is used to invoke class methods:
+ @example
+ DEFAULT.USER> N MYOBJ=$#^%MYCLASS("")
+ DEFAULT.USER> W MYOBJ.MYMETHOD()
+ VALUE
+ @end example
+ @node Public and Private Variables
+ @section Public and Private Variables
+ FreeM supports private fields with the @code{:PRIVATE} specifier in the @code{SET} command, enforcing classical object-oriented data encapsulation. The @code{:PUBLIC} specifier is provided for completeness, and is the default.
+ The below constructor for a @code{FRACTION} class defines two private fields:
+ @example
+ %FRACTION(THIS,INIT):OBJECT ;
+    S THIS("NUMERATOR"):PRIVATE=$P(INIT,"/",1)
+    S THIS("DENOMINATOR"):PRIVATE=$P(INIT,"/",2)
+    Q
+ @end example
- @node Public Variables
+ Either of the following commands will create a public field:
- @subsection Public Variables
- @node Private Variables
+ @example
- @subsection Private Variables
+   S THIS("VARNAM")="Initial Value"
+   S THIS("VARNAM"):PUBLIC="Initial Value"
+ @end example
+ Attempting to access private fields from outside of the class will raise error condition @code{ZOBJFLDACCV}.
+ @node Instantiating Objects
+ @section Instantiating Objects
+ To instantiate an object (i.e., create an object from a certain class), you will use the @code{NEW} command as follows:
+ @example
+ NEW MYSTR=$#^%STRING("myString")
+ @end example
+ This will create a local variable called MYSTR of type STRING, and initialize it with the value myString.
+ @subsection Determining Object Class
+ To determine the class of any FreeM local variable, you will use the @code{$$TYPE()} method:
+ @example
+ USER> W MYSTR.$$TYPE()
+ ^%STRING
+ @end example
+ The @code{$$TYPE()} method is a member of the @code{OBJECT} class.
  @node Libraries
  @chapter Libraries
- Line 4613  To remove the above mapping, any of the
+ Line 5201  To remove the above mapping, any of the
    KILL ^$SYSTEM("MAPPINGS","GLOBAL","^FOO")
  @end example
- @node Transaction Processing
- @chapter Transaction Processing
- @cindex transaction processing
- FreeM implements a significant subset of the transaction processing features from @emph{ANSI X11.1-1995}. This allows a series of global operations to be conducted all at once, either in batch mode (where concurrency is not disturbed), or in serial mode (where writes are guaranteed to be atomic, consistent, isolated, and durable).
- @section Theory of Operation
- FreeM uses a pessimistic concurrency control mechanism for @code{SERIAL} transactions, meaning that any @code{TSTART} command that includes the @code{SERIAL} transaction parameter will cause the process to acquire the transaction processing mutex, which prevents any process but the one holding the mutex from performing any data access (read or write) until either @code{TCOMMIT} or @code{TROLLBACK} is called, either committing or rolling back the transaction, respectively.
- Any transaction in between its @code{TSTART} and @code{TCOMMIT}/@code{TROLLBACK} is said to be @emph{in-flight}. During the in-flight stage, pending global operations are held only in memory and after-image journals.
- FreeM maintains a list of all globals affected during a transaction in-flight. When a @code{TCOMMIT} is reached, FreeM will generate a @emph{checkpoint} of each global data file to be changed by the transaction. These checkpoints allow all FreeM globals to be restored to their pre-transaction state if a @code{TCOMMIT} should fail part of the way through its operation.
- Checkpoints can have one of two modes:
- @table @asis
- @item @code{CP_REMOVE}
- Used for globals that did not exist prior to the beginning of this transaction. Simply marks the entire global data file for deletion in case of @code{TCOMMIT} failure.
- @item @code{CP_RESTORE}
- Used for globals that @emph{did} exist prior to the beginning of this transaction. In this case, the entire global data file is copied to a new file with a @code{.chk} extension. In cases of @code{TCOMMIT} failure, @code{CP_RESTORE} checkpoint files will be restored over the partially-modified live data file.
- @end table
- The below example shows a few global operations and checkpoints for a transaction in-flight using the @code{trantab} direct-mode command:
- @verbatim
- TL1:DEFAULT.USER> trantab
-  $TLEVEL 1*
-   Operations for Transaction ID: 6ea14aad-b8f1-47f9-9f52-4f513f892bc0 [RESTARTABLE SERIAL]
-    OP. NO.   ACTION         KEY/DATA
-    -------   ------         --------
-        SET            ^FOO=3
-        KILL           ^FOO
-        SET            ^snw=10
-        SET            ^BRANDNEW=6
-   Global checkpoints:
-    GLOBAL                        MODE                FILES
-    ------                        ----                -----
-    ^BRANDNEW                     CP_REMOVE           IN:   /usr/local/var/freem/USER/globals/^BRANDNEW
-    ^snw                          CP_RESTORE          IN:   /usr/local/var/freem/USER/globals/^snw
-                                                      OUT:  /usr/local/var/freem/USER/globals/^snw.23390.1.chk
-    ^FOO                          CP_RESTORE          IN:   /usr/local/var/freem/USER/globals/^FOO
-                                                      OUT:  /usr/local/var/freem/USER/globals/^FOO.23390.1.chk
- @end verbatim
- In the above example, @code{IN} files are the live data file that will be overwritten or removed, and @code{OUT} files are the checkpoints themselves. Note that @code{OUT} files are only used for @code{CP_RESTORE} checkpoints.
  @node Asynchronous Event Handling
- Line 5330  Raised when an attempt is made to use a
+ Line 5866  Raised when an attempt is made to use a
  @end table
- @node Debugging
- @chapter Debugging
- @cindex debugging
  @node System Configuration
  @chapter System Configuration
- Line 5341  Raised when an attempt is made to use a
+ Line 5874  Raised when an attempt is made to use a
  @section Installing FreeM
  @cindex installation
- @section Build Configuration
+ @subsection Installation Methods
- @cindex build configuration
- When configuring FreeM with the supplied @code{configure} script, there are some FreeM-specific options that may be used to compile in optional features, or exclude default ones:
+ FreeM allows the following installation methods:
  @table @asis
+ @item Binary Repository
+ On recent versions the Ubuntu and Debian distributions of GNU/Linux, we provide package repositories from which FreeM may easily be installed. See the @emph{FreeM Wiki} for more information, and @emph{https://packages.coherent-logic.com} for instructions.
- @item @code{--enable-mwapigtk} (EXPERIMENTAL)
+ If available, this is the simplest method of installing FreeM.
- Enables experimental support for the M Windowing API using the GTK3 libraries. Requires that you have GTK 3 libraries, their headers, and their dependencies installed on your system.
+ @item Binary Packages
+ We provide binary packages of FreeM for @emph{dpkg} and @emph{rpm}-based distributions of GNU/Linux, and @emph{pkgadd} packages for Solaris 8-10. If you cannot use repositories, this is the easiest option.
+ See @emph{https://freem.coherent-logic.com/binaries.cfm} for downloads and instructions.
+ @item Source Archive
+ If you prefer installing from source, we recommend that you download the latest @emph{.tar.gz} file from @emph{https://freem.coherent-logic.com/downloads.cfm}, and follow these steps:
+ @example
+ $ gunzip freem-@emph{<version>}.tar.gz
+ $ tar xf freem-@emph{<version>}.tar
+ $ cd freem
+ $ ./configure # see the Build Configuration section for optional flags
+ $ make
+ $ sudo make install
+ @end example
- Please consult your operating system's documentation for the correct commands to install the required libraries.
+ Once this process has been completed, you may proceed to @emph{Initial Configuration}.
- @emph{Example}
+ Installation from source archive is the most challenging but flexible supported option for advanced users.
+ @item CVS Repository
+ If you wish to try the bleeding-edge development version of FreeM, you may do so by following these steps:
- @example
+ @verbatim
- $ ./configure --enable-mwapigtk
+ $ cvs -d :pserver:anonymous@cvs.coherent-logic.com:/home/cvsroot co freem
+ $ cd freem
+ $ ./autogen.sh
+ $ ./configure # see the Build Configuration section for optional flags
  $ make
  $ sudo make install
- @end example
+ @end verbatim
- @item @code{--enable-berkeleydb} (EXPERIMENTAL)
+ Once this process has been completed, you may proceed to @emph{Initial Configuration}.
- Enables experimental support for using the BerkeleyDB database as a global handler for FreeM global namespaces. Requires that you have the @code{libdb} library, headers, and dependencies installed on your system.
- Please consult your operating system's documentation for the correct commands to install the required libraries.
+ This installation method is by far the most complicated, and is intended only for those who wish to contribute to FreeM development. It is not intended for end users, and no technical support will be provided.
- @emph{Example}
+ See the @emph{Contributor Guide} on the @emph{FreeM Wiki} for more information.
+ @end table
+ @subsection Build Configuration
+ @cindex build configuration
- @example
+ When configuring FreeM with the supplied @code{configure} script, there are some FreeM-specific options that may be used to compile in optional features, or exclude default ones:
- $ ./configure --enable-berkeleydb
- $ make
- $ sudo make install
- @end example
+ @table @asis
- @item @code{--without-readline}
+ @item @code{--enable-mwapi} (EXPERIMENTAL)
- Builds FreeM without GNU @code{readline} support, even if @code{readline} is installed on your system.
+ Enables experimental support for the M Windowing API (ANSI @emph{X11.6-1995}) using the OSF/Motif widget toolkit. Requires that you have the @code{X11}, @code{Xt}, @code{ICE}, and @code{Xm} libraries, as well as all of their C header files.
- Please note that building FreeM without GNU @code{readline} will also exclude REPL functionality and all direct-mode utility commands, i.e. @code{events}, @code{tdump}, @code{shmstat}, and @code{shmpages}.
+ Please consult your operating system's documentation for the correct commands to install the required libraries.
  @emph{Example}
  @example
- $ ./configure --without-readline
+ $ ./configure --enable-mwapi
  $ make
  $ sudo make install
  @end example
  @end table
+ @subsection Initial Configuration
+ Once FreeM is installed, you will need to configure it:
+ @enumerate
+ @item Create a user and group, each named @emph{freem}, under which FreeM will run
+ @item Add any user accounts that will need to run FreeM to the @emph{freem} group
+ @item Have all users added in step 2 sign out and sign in for the new group membership to take effect
+ @item Run @code{fmadm configure} with superuser privileges to create the @code{DEFAULT} environment with @code{SYSTEM} and @code{USER} namespaces and default after-image journal settings, and populate the bundled vendor routines
+ @item Run @code{fmadm start environment} with superuser privileges to start the @code{DEFAULT} environment
+ @item Make sure the environment is ready by running @code{fmadm status environment} with superuser privileges
+ @end enumerate
+ @subsubsection Creating Additional Environments
+ To create additional environments, do the following steps:
+ @enumerate
+ @item Create a new user and group for the environment @emph{(optional)}
+ @item Run @code{fmadm configure -e=@emph{<environment>} -u=@emph{<username>} -g=@emph{<groupname>} [-E=@emph{true|false}]} @emph{(the @code{-E} flag enables or disables the environment)}
+ @item Run @code{fmadm start environment -e=@emph{<environment>}} to start the environment
+ @item Run @code{fmadm status environment} to make sure the environment is healthy
+ @end enumerate
+ @subsubsection Additional Customization
+ See the FreeM @emph{environment catalog} at @code{@emph{$PREFIX}/etc/freem/env.conf}, and the @emph{fmadm}(1) @code{man} page for more information.
+ @emph{$PREFIX} represents the root location of your FreeM installation. This can be @code{/usr/local}, @code{/}, or others, depending on how FreeM was built and installed.
  @node Accessing FreeM from C Programs
  @chapter Accessing FreeM from C Programs

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