Question

How to count the number of digits in an integer with Pascal

Answer 1

program DigitCounterString;

{$mode delphi}{$H+}

uses
  SysUtils; // IntToStr

function CountDigitsString(value: Integer): Integer;
var
  text: string;
begin
  // Convert the number to a string
  text := IntToStr(value);

  // If negative, ignore the leading '-'
  if (Length(text) > 0) and (text[1] = '-') then
    Result := Length(text) - 1
  else
    Result := Length(text);
end;

var
  number, digits: Integer;

begin
  number := -12345;
  digits := CountDigitsString(number);

  WriteLn('Number: ', number);
  WriteLn('Digit count (String method): ', digits);
end.



{
run:

Number: -12345
Digit count (String method): 5

}

 

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Answer 2

program DigitCounterLog10;

{$mode delphi}{$H+}

uses
  Math;

function CountDigitsLog10(value: Integer): Integer;
var
  num: Integer;
begin
  num := Abs(value);

  // Zero must be handled explicitly
  if num = 0 then
  begin
    Result := 1;
    Exit;
  end;

  // Use floor(log10(n)) + 1
  Result := Floor(Log10(num)) + 1;
end;

var
  number, digits: Integer;

begin
  number := 987654321;
  digits := CountDigitsLog10(number);

  WriteLn('Number: ', number);
  WriteLn('Digit count (log10 method): ', digits);
end.


{
run:

Number: 987654321
Digit count (log10 method): 9

}

 

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