CASE statement question

[Elmug]

RealX being a real, can't seem to make this work:

Case RealX of
<> 1 :  IsNotOne;
 =  1 :  IsOne,;
  <  1 : LessThanOne ;
 >  1 :  IllegalOperation;
 end;


IsNotOne, IsOne, etc. are the code to do as per value of RealX. Looks like this is not allowed?

If so, how?

Thanks!
   

[eny]

Case only works with ordinal types.
http://www.freepascal.org/docs-html/ref/refsu47.html
Contrary to what is mentioned in the manual, it does work with booleans (which is an ordinal type).

[Elmug]

Thanks Eny...

I'll do it with if statements then, unless some other way is pointed out to.

[IPguy]

I occasionally wish there was a "caseSTR <string> of" construct.
It would make my code easier to read rather than having a bunch of if then/else statements.

I did run across this 2002 conversation on the fpc list:
http://lists.freepascal.org/lists/fpc-pascal/2002-February/002799.html

Case with strings is not supported, and probably will never be
supported. One way of doing the above is to

Code: [Select]

const
   N = 3;
   names : Array [1..N] string [10] = ('abcdeefdre','gfsgeyeyey','jfmvnvyret');

Var
  I,Which : Integer;

begin
  I:=1;
  Which:=0;
  While (Which=0) and (I<=N) do
    If Names[I]=ParamStr(1) then
      Which:=I
    else
      Inc(I);
  Case Which of
   1 : ;
   2 : ;
   3 : ;
  else
    // Zero, invalid option.
  end


[garlar27]

@Elmug: If you need a simple comparisson you can do the following:

Code: Pascal  [Select][+][-]

1. { CompareValue is in Math unit }
2. i := 1;
3. case CompareValue(RealX, i) of
4.    -1: { RealX is Minor than i } LessThanOne;
5.    0: { RealX is Equal to i } IsOne;
6.    1: { RealX is Bigger than i } IllegalOperation;
7. end;
8.  

[Blaazen]

@ IPguy

I occasionally wish there was a "caseSTR <string> of" construct.
It would make my code easier to read rather than having a bunch of if then/else statements.

I did run across this 2002 conversation on the fpc list:
http://lists.freepascal.org/lists/fpc-pascal/2002-February/002799.html

But it is from 2002 ! 

Times changed, we have 2011.

This already works, at least one year ! (It didn't work in fpc 2.4.2 but it was available in SVN).

Code: [Select]

var str: string;
begin
  case str of
  'january': ;
  'february': ;
  'march': ;
  end; 


[IPguy]

Good news !!  Blaazen - Thanks for the update.

... and more work to do - now to rip out working code and implement this.
However, the readability gains are worth the short term effort.

[Elmug]

Great tips. I can put the comparevalue to use right away, and the case string is also very useful.

Big Thanks !