check string for numbers

I have a written a DLL which returns strings and integers from string. I am having a problem whereby if the string does not contain a valid number the real type conversion fails. What I need is a if else statement that checks there is a valid number.

Function lenofcall(S1,S2 : String) :Real;

Begin
Result := (StrToFloat(copy(S1,1,2))*60)+(StrToFloat(copy(S1,4,2)));
end

 for instance the following text would give a result of 129
S1 := '01:59'

but if
S1 := '----' or any other non number text,
then I want the result to give a result of '0'

any Ideas


lloydie-tAsked:
Who is Participating?
 
Wim ten BrinkConnect With a Mentor Self-employed developerCommented:
Oh, and since we want to result 0 if we don't have a valid time:

var
  Hour, Min, Sec, MSec: Word;
begin
  try
    DecodeTime( StrToTime( '01:59' ), Hour, Min, Sec, MSec );
    Result := Hour * 60 + Min;
  except Result := 0;
  end;
end;

Life isn't difficult if you think logical.
0
 
Ferruccio AccalaiSenior developer, analyst and customer assistance Commented:
just put it in a try except...

Function lenofcall(S1,S2 : String) :Real;
Begin
   try
      Result := (StrToFloat(copy(S1,1,2))*60)+(StrToFloat(copy(S1,4,2)));
   except
      Result := 0;
   end;
end;
0
 
BalsheCommented:
HI
Try this

Function String_TO_REAL(STR:STRING):Real;
Const Number_Str='0123456789.';
Var
  Alpha:String;
  i:Integer;
Begin
  for i :=0 to length(Str) do
    Begin
      if pos(str[i],Number_Str)>0 then
       Alpha:=Alpha+str[i];
    end;
  Result:=StrToFloat(Alpha);
end;
0
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BalsheCommented:

Function String_TO_REAL(STR:STRING):Real;
Const Number_Str='0123456789.';
Var
  Alpha:String;
  i:Integer;
Begin
  for i :=1 to length(Str) do               // start from 1 not from 0
    Begin
      if pos(str[i],Number_Str)>0 then
       Alpha:=Alpha+str[i];
    end;
  Result:=StrToFloat(Alpha);
end;
0
 
Wim ten BrinkSelf-employed developerCommented:
For those who haven't noticed this: lloydie-t wants to convert a string containing a time to a number of minutes. So:

var
  Hour, Min, Sec, MSec: Word;
begin
  DecodeTime( StrToTime( '01:59' ), Hour, Min, Sec, MSec );
  Result := Hour * 60 + Min;
end;

And the result is 119, not 129... ;-)
0
 
lloydie-tAuthor Commented:
Nearly there Alex, I have tried your code, but it does raise an excption when the string is not in a time format
FI: |SBNode is not a valid time.

this is the code I'm using

Function LenOfCall (S1,S2: String): Real; stdcall;
var
Hour, Min, Sec, Msec:Word;
Begin
        try
        DecodeTime(strToTime(copy(S1,50,8)),Hour,Min,Sec,Msec);
        Result := Hour*60+Min+Sec/60;
        except
        Result := 0;
        end;
end;

but it is much neater. Any other ideas


0
 
lloydie-tAuthor Commented:
Seems as though the debugger is working overtime. The exception is raised only when running the app in delphi, running it stand alone does'nt seem to cause a problem.
0
 
Wim ten BrinkSelf-employed developerCommented:
That might be related to the locale settings, the date-time separator. :-) But you could just use: S1[3] := ':';
And then use my solution to convert it.

Oh, and why: strToTime(copy(S1,50,8)) ???
You're copying 8 characters but the time would just be 5 characters. Maybe use: strToTime(copy(S1,50,5))
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lloydie-tAuthor Commented:
The exception only happens when I receive a string such as '----------' or '|SBNode'. I read somewhere that the debugger can sometimes pick these up even when using 'try except'. Otherwise It seems to work OK and as expected, when not running in delphi using the same data.

Thanks fro your help.
0
 
Wim ten BrinkSelf-employed developerCommented:
Ehm, yes. The debugger picks up exceptions if you've set it up like that in de debug options under the Tools menu. Then the debugger stops at the exception, but if you press F9 it will just let the application handle it further. You'd have to turn that "Break on exception" option off if you don't want that.
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