TryStrToFloat

[BubikolRamios]

Hmm, no message. Note there is nothing after '.'.
I assume it thinks strtofloat('0.') is 0. How to check then if string or decimal ?

Code: Pascal  [Select][+][-]

1. var
2.   fs: TFormatSettings;
3.   x: Float;
4. begin
5.   x := NaN;
6.   fs := FormatSettings;
7.   fs.DecimalSeparator := '.';  
8.  
9.  
10.   if not TryStrToFloat('0.',x, fs)then
11.   begin
12.     showmessage('foo');
13.   end;        
14.  

[paweld]

if the TryStrToFloat function returns TRUE, it means that the string was successfully converted to a number, and if FALSE, the conversion failed.

Code: Pascal  [Select][+][-]

1. var
2.   fs: TFormatSettings;
3.   x: Double;
4. begin
5.   fs.DecimalSeparator := '.';
6.   if TryStrToFloat('0.', x, fs) then
7.     ShowMessage('It''s float: ' + FloatToStr(x))
8.   else
9.     showmessage('It'' string');
10. end;          

[Thaddy]

Should it not be '0.0';?
I mean it is not called a separator for nothing: it expects two decimal values either side of the dot.

[BubikolRamios]

Should it not be '0.0';?
I mean it is not called a separator for nothing: it expects two decimal values either side of the dot.

Checking that OnKeyUp on TEdit control... Press backspace on something like '0.2'

[BubikolRamios]

test:

Code: Pascal  [Select][+][-]

1. showmessage(FloatToStr(StrToFloat('0.'))); //--> 0
2. showmessage(FloatToStr(StrToFloat('01')));//--> 1          
3.  

Not very logical.

[wp]

I mean it is not called a separator for nothing: it expects two decimal values either side of the dot.

Even good-old Turbo Pascal detects '0.' as 0, and '.1' as 0.1

There's nothing wrong with these numbers (go to the U.S., or look at an Americal Youtube math-related video, and you'll see them all over the place).

[Zvoni]

?!?!?!?
TryStrToFloat calls TextToFloat, which calls Val

Code: Pascal  [Select][+][-]

1. program Project1;
2. Uses Sysutils;
3. Var
4.   x:Double;
5.   fs: TFormatSettings;
6. begin
7.   fs:=FormatSettings;
8.   fs.DecimalSeparator:='.';
9.   Writeln(TryStrToFloat('0.',x,fs),' = ',x);
10. end.

Returns

Code: [Select]

TRUE =  0.0000000000000000E+000

[Warfley]

The sysutil conversion functions all rely on the internal call to the val directive, which does a few interesting things. Basically it can parse everything that you can write into your pascal code as number constant, and even more:

Code: Pascal  [Select][+][-]

1.   val('$FF', i, err);
2.   val('%10', i, err);
3.   val('&43', i, err);
4.   val('1.', d, err);
5.   val('.1', d, err);
6.   val('3e4', d, err);

If you want only "normal" number notation, you should simply write your own function:

Code: Pascal  [Select][+][-]

1. type
2.   TNumberType = (ntNotANumber, ntInteger, ntFloat);
3.  
4. function isNumber(const AString: String): TNumberType;
5. var
6.   c: Char;
7. begin
8.   if Length(AString) = 0 then
9.     Exit(ntNotANumber);
10.   Result := ntInteger;
11.   for c in AString do
12.     if (c='.') and (Result=ntInteger) then
13.       Result:=ntFloat
14.     else if not (c in ['0'..'9']) then
15.       Exit(ntNotANumber);
16. end;

Which you can further customize to your liking (e.g. by adding a last if statement to rule out a . without followup)

[Bart]

The sysutil conversion functions all rely on the internal call to the val directive, which does a few interesting things. Basically it can parse everything that you can write into your pascal code as number constant, and even more:

And it can even parse enums.

Bart

[jcmontherock]

"StrToFloatDef", "StrToIntDef" could also be used

[BubikolRamios]

"StrToFloatDef", "StrToIntDef" could also be used

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

Code: Pascal  [Select][+][-]

1.   fs := FormatSettings;
2.   fs.DecimalSeparator := '.';
3.  
4.  
5.   if StrToFloatDef('dfsdf',-100000, fs) = -100000 then
6.   begin
7.     Exit;
8.   end;    
9.  
10.  

[dseligo]

"StrToFloatDef", "StrToIntDef" could also be used

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

Code: Pascal  [Select][+][-]

1.   fs := FormatSettings;
2.   fs.DecimalSeparator := '.';
3.  
4.  
5.   if StrToFloatDef('dfsdf',-100000, fs) = -100000 then
6.   begin
7.     Exit;
8.   end;    
9.  
10.  

I get 'exit' on my screen:

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. uses SysUtils;
4.  
5. var
6.   fs: TFormatSettings;
7.  
8. begin
9.   fs := FormatSettings;
10.   fs.DecimalSeparator := '.';
11.  
12.   if StrToFloatDef('dfsdf',-100000, fs) = -100000 then
13.   begin
14.     WriteLn('exit');
15.     Exit;
16.   end;
17.  
18.   WriteLn('end');
19. end.

[TRon]

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

Which is exactly working as advertised:

StrToFloatDef tries to convert the string S to a floating point value, and returns this value. If the conversion fails for some reason, the value Default is returned instead.

[dseligo]

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

Which is exactly working as advertised:

StrToFloatDef tries to convert the string S to a floating point value, and returns this value. If the conversion fails for some reason, the value Default is returned instead.

But he said it doesn't return default:

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

[TRon]

But he said it doesn't return default:

That is not exactly 100% TS' words

on if line it does nothing does not go paste if, does not go into exit, nothing. No errors or exceptions. ?

Indeed: "it does not go into exit" and "it does nothing" (with the conclusion, no errors or exceptions).

Last part is covered by the documentation as linked.

The statement "it does nothing" can be analyzed as follows: the first line that gets executed when the condition is met is the line containing the exit statement. In the particular example of TS, the condition is true thus exit gets executed (as shown per your example as well). And indeed that does nothing (further) except for executing the exit statement (no idea what TS is expecting to happen).

The statement "it does not go into exit" deserves further explanation from TS, because the context is important there. An exit statement only exits a function (and if that function happens to be the main function it will exit the program). With the code as shown by TS it is impossible for TS to conclude that the exit statement is not executed.