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#############################################################################
##
#W reread.g GAP Library Steve Linton
##
##
#Y Copyright (C) 1996, Lehrstuhl D für Mathematik, RWTH Aachen, Germany
#Y (C) 1998 School Math and Comp. Sci., University of St Andrews, Scotland
#Y Copyright (C) 2002 The GAP Group
##
## This file contains the Reread function and its relatives
## RereadLib, etc.
##
## Seems rather little for a file by itself, but I can see no other
## natural home
##
#############################################################################
##
## <#GAPDoc Label="Reread">
##
## <ManSection>
## <Func Name="Reread" Arg='filename'/>
## <Var Name="REREADING"/>
##
## <Description>
## In general, it is not possible to read the same &GAP; library file
## twice, or to read a compiled version after reading a &GAP; version,
## because crucial global variables are made read-only
## (see <Ref Sect="More About Global Variables"/>)
## and filters and methods are added to global tables.
## <P/>
## A partial solution to this problem is provided by the function
## <Ref Func="Reread"/> (and related functions <C>RereadLib</C> etc.).
## <C>Reread( <A>filename</A> )</C> sets the global variable
## <Ref Var="REREADING"/> to <K>true</K>,
## reads the file named by <A>filename</A> and then resets
## <Ref Var="REREADING"/>.
## Various system functions behave differently when <Ref Var="REREADING"/>
## is set to <K>true</K>.
## In particular, assignment to read-only global variables is permitted,
## calls to <Ref Func="NewRepresentation"/>
## and <Ref Func="NewInfoClass"/> with parameters identical to those
## of an existing representation or info class will return the existing
## object, and methods installed with
## <Ref Func="InstallMethod"/> may sometimes displace
## existing methods.
## <P/>
## This function may not entirely produce the intended results,
## especially if what has changed is the super-representation of a
## representation or the requirements of a method. In these cases, it is
## necessary to restart &GAP; to read the modified file.
## <P/>
## An additional use of <Ref Func="Reread"/> is to load the compiled version
## of a file for which the &GAP; language version had previously been read
## (or perhaps was included in a saved workspace).
## See <Ref Label="Kernel modules"/> and
## <Ref Sect="Saving and Loading a Workspace"/> for more information.
## <P/>
## It is not advisable to use <Ref Func="Reread"/> programmatically.
## For example, if a file that contains calls to <Ref Func="Reread"/>
## is read with <Ref Func="Reread"/> then <Ref Var="REREADING"/> may be
## reset too early.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
BindGlobal("Reread",
function(arg)
local res;
MakeReadWriteGlobal("REREADING");
REREADING := true;
MakeReadOnlyGlobal("REREADING");
if LEN_LIST(arg) > 1 then
res := CallFuncList( Read, arg );
else
CallFuncList( Read, arg );
fi;
MakeReadWriteGlobal("REREADING");
REREADING := false;
MakeReadOnlyGlobal("REREADING");
if LEN_LIST(arg) > 1 then
return res;
fi;
end);
BindGlobal("RereadAndCheckFunc",
function( arg )
local func;
func := CallFuncList(ReadAndCheckFunc, arg);
return function( arg )
local res;
MakeReadWriteGlobal("REREADING");
REREADING := true;
MakeReadOnlyGlobal("REREADING");
if LEN_LIST(arg) > 1 then
res := CallFuncList(func,arg);
else
CallFuncList(func,arg);
fi;
MakeReadWriteGlobal("REREADING");
REREADING := false;
MakeReadOnlyGlobal("REREADING");
if LEN_LIST(arg) > 1 then
return res;
fi;
end;
end);
#############################################################################
##
#F RereadLib( <name> ) . . . . . . . . . . . . . . . . . . . . . library files
##
BIND_GLOBAL("RereadLib",RereadAndCheckFunc("lib"));
#############################################################################
##
#F RereadGrp( <name> ) . . . . . . . . . . . . . . . . . . group library files
##
BIND_GLOBAL("RereadGrp",RereadAndCheckFunc("grp"));
#############################################################################
##
#E
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