[fpc-pascal] Calling a function by name (as string) read froma text file

[Tomas Hajny]

Jilani Khaldi wrote:
>> Did you implement the record exactly as shown? This error normally
>> occurs
>> if you have fields in your record that you don't mention in your typed
>> const declaration.
>
> {$mode objfpc} -> Error!
> {$mode delphi} -> Ok!
> ...
> type
>    TSetupFuncMapping = record
>      x: array of double;
>      name:string;
>      func: SetupFunc;
>    end;
>
> const
>    SFM: array[0..2] of TSetupFuncMapping = (
>    (x: nil; name: 'SetupFunction_1'; func: SetupFunction_1),
>    (x: nil; name: 'SetupFunction_2'; func: SetupFunction_2),
>    (x: nil; name: 'SetupFunction_3'; func: SetupFunction_3));


I only get a RTE when compiling and running the following with 2.0.4, not
a compile time error.

Tomas


{$MODE OBJFPC}
uses
   SysUtils;

type
   SetupFun = function(const vect: array of double): double;

MyRec = record
   x: array of double;
   myFunName: ShortString; // function name to evoke
end;

type
   TSetupFuncMapping = record
     x: array of double;
     name:string;
     func: SetupFun;
   end;

function SetupFunction_1 (const vect: array of double): double;
begin
 SetupFunction_1 := 1;
end;

function SetupFunction_2 (const vect: array of double): double;
begin
 SetupFunction_2 := 2;
end;

function SetupFunction_3 (const vect: array of double): double;
begin
 SetupFunction_3 := 3;
end;

function SetMeUp(const x1: array of double): double;
var
   i: integer;
   sum: double;
begin
   sum := 0.0;
   for i := 0 to High(x1) do
     sum := sum + x1[i];
   result := sum;
end;


const
   SFM: array[0..3] of TSetupFuncMapping = (
   (x: nil; name: 'SetupFunction_1'; func: @SetupFunction_1),
   (x: nil; name: 'SetupFunction_2'; func: @SetupFunction_2),
   (x: nil; name: 'SetMeUp'; func: @SetMeUp),
   (x: nil; name: 'SetupFunction_3'; func: @SetupFunction_3));

// main
var
   MR: MyRec;
   y: double;
   st: string;
   f: text;
   i, j, count: integer;
begin
   // read MR from a text file...
   assign(f, 'data.txt');
   {$I-}
   reset(f);
   {$I+}
   readln(f, MR.myFunName);
   readln(f, count);
   setlength(MR.x,count+1);
   for i := 0 to count do
     readln(f, MR.x[i]);
   closefile(f);
   writeln(MR.myFunName);
   writeln(High(MR.x));
   for i := 0 to High(MR.x) do
     begin
      writeln(MR.x[i]);
      for J := 0 to 3 do
       if SFM [J].Name = MR.MyFunName [J] then
        y := SFM [J].Func (MR.X);
      st := Format('Value: %6.5f', [y]);
      writeln(st);
      setlength(MR.x,0);
     end;
   readln;
end.