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#############################################################################
##
## This file is part of GAP, a system for computational discrete algebra.
## This file's authors include Steve Linton.
##
## Copyright of GAP belongs to its developers, whose names are too numerous
## to list here. Please refer to the COPYRIGHT file for details.
##
## SPDX-License-Identifier: GPL-2.0-or-later
##
##
## This file contains the second stage of the "public" interface to
## the global variable namespace, allowing globals to be accessed and
## set by name.
##
## This is defined in two stages. global.g defines "capitalized" versions
## of the functions which do not use Info or other niceties and are not
## set up with InstallGlobalFunction. This can thus be read early, and
## the functions it defines can be used to define functions used to read
## more of the library.
##
## This file and global.gi stages install the really "public"
## functions and can be read later (once Info, DeclareGlobalFunction,
## etc are there)
##
## All of these functions give a warning if the global variable name
## contains characters not recognised as part of identifiers by the
## GAP parser
##
#############################################################################
##
#F IsValidIdentifier( <str> ) . . . check if a string is a valid identifier
##
## <#GAPDoc Label="IsValidIdentifier">
## <ManSection>
## <Func Name="IsValidIdentifier" Arg='str'/>
##
## <Description>
## returns <K>true</K> if the string <A>str</A> would form a valid identifier
## consisting of letters, digits and underscores; otherwise it returns
## <K>false</K>. It does not check whether <A>str</A> contains characters escaped by a
## backslash <C>\</C>.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction("IsValidIdentifier");
#############################################################################
##
#F ValueGlobal( <name> ) . . . . . . . . . . . access a global by its name
##
## <ManSection>
## <Func Name="ValueGlobal" Arg='name'/>
##
## <Description>
## ValueGlobal ( <A>name</A> ) returns the value currently bound to the global
## variable named by the string <A>name</A>. An error is raised if no value
## is currently bound
## </Description>
## </ManSection>
##
DeclareGlobalFunction("ValueGlobal");
#############################################################################
##
#F IsBoundGlobal( <name> ) . . . . . check if a global is bound by its name
##
## <ManSection>
## <Func Name="IsBoundGlobal" Arg='name'/>
##
## <Description>
## IsBoundGlobal ( <A>name</A> ) returns true if a value is currently bound
## to the global variable named by the string <A>name</A> and false otherwise
## </Description>
## </ManSection>
##
DeclareGlobalFunction("IsBoundGlobal");
#############################################################################
##
#F IsAutoGlobal( <name> ) . . . . . check if a global is automatic
##
## <ManSection>
## <Func Name="IsAutoGlobal" Arg='name'/>
##
## <Description>
## IsAutoGlobal ( <A>name</A> ) returns true if there is a global variable
## named <A>name</A>, declared using
## <Ref Func="DeclareAutoreadableVariables"/>, which has not yet been
## accessed. This means reading this variable's value will cause code
## to be executed.
## </Description>
## </ManSection>
##
DeclareGlobalFunction("IsAutoGlobal");
#############################################################################
##
#F UnbindGlobal( <name> ) . . . . . . . . . . unbind a global by its name
##
## <ManSection>
## <Func Name="UnbindGlobal" Arg='name'/>
##
## <Description>
## UnbindGlobal ( <A>name</A> ) removes any value currently bound
## to the global variable named by the string <A>name</A>. Nothing is returned
## <P/>
## A warning is given if <A>name</A> was not bound
## The global variable named by <A>name</A> must be writable,
## otherwise an error is raised.
## </Description>
## </ManSection>
##
DeclareGlobalFunction("UnbindGlobal");
#############################################################################
##
#F IsReadOnlyGlobal( <name> ) . determine if a global variable is read-only
##
## <ManSection>
## <Func Name="IsReadOnlyGlobal" Arg='name'/>
##
## <Description>
## IsReadOnlyGlobal ( <A>name</A> ) returns true if the global variable
## named by the string <A>name</A> is read-only and false otherwise (the default)
## </Description>
## </ManSection>
##
DeclareGlobalFunction("IsReadOnlyGlobal");
#############################################################################
##
#F IsConstantGlobal( <name> ) . determine if a global variable is constant
##
## <ManSection>
## <Func Name="IsConstantGlobal" Arg='name'/>
##
## <Description>
## IsConstantGlobal ( <A>name</A> ) returns true if the global variable
## named by the string <A>name</A> is constant and false otherwise (the default).
## </Description>
## </ManSection>
##
DeclareGlobalFunction("IsConstantGlobal");
#############################################################################
##
#F MakeReadOnlyGlobal( <name> ) . . . . . make a global variable read-only
##
## <ManSection>
## <Func Name="MakeReadOnlyGlobal" Arg='name'/>
##
## <Description>
## MakeReadOnlyGlobal ( <A>name</A> ) marks the global variable named
## by the string <A>name</A> as read-only.
## <P/>
## A warning is given if <A>name</A> has no value bound to it or if it is
## already read-only
## </Description>
## </ManSection>
##
DeclareGlobalFunction("MakeReadOnlyGlobal");
#############################################################################
##
#F MakeReadWriteGlobal( <name> ) . . . . make a global variable read-write
##
## <ManSection>
## <Func Name="MakeReadWriteGlobal" Arg='name'/>
##
## <Description>
## MakeReadWriteGlobal ( <A>name</A> ) marks the global variable named
## by the string <A>name</A> as read-write
## <P/>
## A warning is given if <A>name</A> is already read-write
## </Description>
## </ManSection>
##
DeclareGlobalFunction("MakeReadWriteGlobal");
#############################################################################
##
#F MakeConstantGlobal( <name> ) . . . . . make a global variable constant
##
## <#GAPDoc Label="MakeConstantGlobal">
## <ManSection>
## <Func Name="MakeConstantGlobal" Arg='name'/>
##
## <Description>
## MakeConstantGlobal ( <A>name</A> ) marks the global variable named
## by the string <A>name</A> as constant. A constant variable can never
## be reassigned or made read-write again.
## <P/>
## A warning is given if <A>name</A> is already constant.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction("MakeConstantGlobal");
#############################################################################
##
#F BindGlobal( <name>, <val> ) . . . . . . sets a global variable `safely'
##
## <#GAPDoc Label="BindGlobal">
## <ManSection>
## <Func Name="BindGlobal" Arg='name, val'/>
## <Func Name="BindConstant" Arg='name, val'/>
##
## <Description>
## <Ref Func="BindGlobal"/> and <Ref Func="BindConstant"/> set the global
## variable named by the string <A>name</A> to the value <A>val</A>,
## provided that variable is writable. <Ref Func="BindGlobal"/> makes
## the resulting variable read-only, while <Ref Func="BindConstant"/> makes
## it constant.
## If <A>name</A> already had a value, a warning message is printed.
## <P/>
## This is intended to be the normal way to create and set <Q>official</Q>
## global variables (such as operations, filters and constants).
## <P/>
## Caution should be exercised in using these functions, especially
## <Ref Func="UnbindGlobal"/> as unexpected changes
## in global variables can be very confusing for the user.
## <P/>
## <Example><![CDATA[
## gap> xx := 16;
## 16
## gap> IsReadOnlyGlobal("xx");
## false
## gap> ValueGlobal("xx");
## 16
## gap> IsBoundGlobal("xx");
## true
## gap> BindGlobal("xx",17);
## #W BIND_GLOBAL: variable `xx' already has a value
## gap> xx;
## 17
## gap> IsReadOnlyGlobal("xx");
## true
## gap> MakeReadWriteGlobal("xx");
## gap> Unbind(xx);
## ]]></Example>
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction("BindGlobal");
DeclareGlobalFunction("BindConstant");
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