[GAP Forum] Is there a simple way to view the source of the function (ex. IsSolvable)?

[buynnnmmm1 at yahoo.co.jp]

Dear Stefan Kohl,

It's wonderful! It's great!
Thank you very much for your help!

P.S.
I resent same e-mail, because I forgot cc:.

With best regards



----- Original Message -----
> From: Stefan Kohl <stefan at mcs.st-and.ac.uk>
> To: Stephen Linton <steve.linton at st-andrews.ac.uk>
> Cc: buynnnmmm1 at yahoo.co.jp; support at gap-system.org
> Date: 2014/9/17, Wed 08:05
> Subject: Re: [GAP Forum] Is there a simple way to view the source of the      function (ex. IsSolvable)?
> 
> On Tue, September 16, 2014 10:53 pm, Stephen Linton wrote:
>>  The thing is that IsSolvable is not really a single function, it is an 
> Operation.
>> 
>>  An Operation in GAP is a collection of functions called Methods that can be 
> used to
>>  compute the result for different kinds of objects.
>> 
>>  You can get the actual Method applied to particular objects via 
> “ApplicableMethod”. For
>>  instance:
>> 
>>  gap> g := SymmetricGroup(5);
>>  Sym( [ 1 .. 5 ] )
>>  gap> ApplicableMethod(IsSolvableGroup,[g]);
>>  function( G ) ... end
>>  gap> f := last;
>>  function( G ) ... end
>>  gap> Print(f);
>>  function ( G )
>>      local  pcgs;
>>      pcgs := TryPcgsPermGroup( G, false, false, true );
>>      if IsPcgs( pcgs )  then
>>          SetIndicesEANormalSteps( pcgs, pcgs!.permpcgsNormalSteps );
>>          SetIsPcgsElementaryAbelianSeries( pcgs, true );
>>          if not HasPcgs( G )  then
>>              SetPcgs( G, pcgs );
>>          fi;
>>          if not HasPcgsElementaryAbelianSeries( G )  then
>>              SetPcgsElementaryAbelianSeries( G, pcgs );
>>          fi;
>>          return true;
>>      else
>>          return false;
>>      fi;
>>      return;
>>  end
>>  gap> FilenameFunc(f);
>>  "/Users/sal/HG/gap/lib/grpperm.gi"
>>  gap> StartlineFunc(f);
>>  1221
>> 
>>  So the Method that would apply to this particular group is found in 
> grpperm.gi starting
>>  at line 1221 (in my development version of GAP).
> 
> A slightly more direct approach is with PageSource:
> 
> gap> PageSource(ApplicableMethod(IsSolvableGroup,[SymmetricGroup(5)]));
> Showing source in /cygdrive/c/GAP/GAP4R7/lib/grpperm.gi (from line 1216)
> #############################################################################
> ##
> #M  IsSolvableGroup( <G> )  . . . . . . . . . . . . . . . .  solvability 
> test
> ##
> InstallMethod( IsSolvableGroup,"for permgrp", true, [ IsPermGroup ], 
> 0,
> function(G)
> local pcgs;
>   pcgs:=TryPcgsPermGroup( G, false, false, true );
>   if IsPcgs(pcgs) then
>     SetIndicesEANormalSteps(pcgs,pcgs!.permpcgsNormalSteps);
>     SetIsPcgsElementaryAbelianSeries(pcgs,true);
>     if not HasPcgs(G) then
>       SetPcgs(G,pcgs);
>     fi;
>     if not HasPcgsElementaryAbelianSeries(G) then
>       SetPcgsElementaryAbelianSeries(G,pcgs);
>     fi;
>     return true;
>   else
>     return false;
>   fi;
> end);
> 
>     Stefan
>