`GAP.evalstr` eats up all output

[fingolfin]

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Consider this:

julia> GAP.evalstr("Display(1);")

julia>

There is no output because GAP.evalstr is currently implemented using GAP.evalstr_ex, which deliberately redirects GAP's stdout into a string:

julia> GAP.evalstr_ex("Display(1);")
GAP: [ [ true,, false,, "1\n" ] ]

Perhaps we should just print this captured stdout? Or perhaps we should implement GAP.evalstr differently. Right now it is implemented using GAP_EvalString which in turn invokes READ_ALL_COMMANDS(instream, False, True, viewObjFunc); -- the first False turns off echo mode; perhaps we should directly invoke GAP.Globals.READ_ALL_COMMANDS, e.g.

function myevalstr(s::String)
  input = GAP.Globals.InputTextString(GAP.Obj(s))
  view = GAP.Globals.EvalString(g"function(x) ViewObj(x); Print(\"\\n\"); end")
  res = GAP.Globals.READ_ALL_COMMANDS(input, true, false, view);
end

I guess it also depends a bit on the desired semantics... Which we should decide on and document more carefully?

[ThomasBreuer]

It really depends on what we want to achieve. Concerning GAP.evalstr("Display(1);"), GAP's Display has no return value, just a side effect, hence GAP.evalstr returns nothing.

GAP.evalstr_ex covers both aspects, return value and output, like in the following example.

julia> GAP.evalstr_ex( "1 + 2;" )
GAP: [ [ true, 3, false,, "3" ] ]

julia> GAP.evalstr_ex( "1 + 2;;" )
GAP: [ [ true, 3, true,, "" ] ]