CODEWITHSUNDEEP
delphidelphi-xe4
user3038442
user3038442

Reputation:

Detect if string contains a float?

How can I detect if a string contains a float. For example: '0.004'

But without using StrToFloat because that function are slow but rather by iterating through chars. 

function IsInteger(const S: String): Boolean;
var
  P: PChar;
begin
  P := PChar(S);
  Result := True;
  while not (P^ = #0) do
  begin
    case P^ of
      '0'..'9': Inc(P);
    else
      Result := False;
      Break;
    end;
  end;
end;

This will check if string is a positive integer but not a float..

Upvotes: 2

Views: 5516

Answers (3)

Leonardo Herrera
Leonardo Herrera

Reputation: 8406

The problem with this question is that saying "is too slow" doesn't tell much. What does the profiler tells to you? Do you have an informed idea about the input data? What about different notations, for example, 6.02e23?

If your input data is mostly noise, then using regular expressions (as answered here) may improve things but only as a first filter. You could then add a second step to actually obtain your number, as explained by David's answer.

Upvotes: 0

user3038458
user3038458

Reputation: 81

Can you use a RegEx here? Something like:

([+-]?[0-9]+(?:\.[0-9]*)?)

Upvotes: 2

David Heffernan
David Heffernan

Reputation: 612963

I would use TryStrToFloat():

if TryStrToFloat(str, value, FormatSettings) then
  ....

If you are prepared to use the default system wide format settings then you can omit the final parameter:

if TryStrToFloat(str, value) then
  ....

Upvotes: 7

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