Int32 on input should have specified numbers count on output

[WojTec]

Hi,

I have another question for you.

On input I have a number <> 0, eg. -542, 4558846, 95423, -55487130 (Int32). On output I want to specified number of input digits whithout converting to string (trim or extend if needed), eg. if digits count = 5 for above numbers output will be:

-55487130 --> 55487 (if < 0 then call Abs())
-542 --> 54200 (if number is < than counter then fill with 0)
4558846 --> 45588
95423 --> 95423

Do you have some idea how can do it?

[DeddyH]

A simple solution:

Delphi-Quellcode:

function Number5Digits(aNumber: integer): Cardinal;
begin
  Result := abs(aNumber);
  while Result > 99999 do
    Result := Result div 10;
  while Result < 10000 do
    Result := Result * 10;
end;

[WojTec]

Thanks :) And what about something like this:

Delphi-Quellcode:

function NumberDigits(ANumber: Int32; ADigits: Byte = 5): Cardinal;

:)

[jfheins]

0. Use Abs()
1. Use log(aNumber) (base 10) to get the number of digits
2. x = ADigits - (result of 1.)
3. Result = ANumber * Math.Power(10, (result of 2.));

Just curious: What ist the reason for this? Output with fixed number of significant figures?

[DeddyH]

Or something like this:

Delphi-Quellcode:

uses math;

function NumberToDigits(aNumber: integer; Digits: Byte = 5): Cardinal;
var RangeMin, RangeMax: Cardinal;
begin
  if Digits < 1 then
    raise Exception.Create('What number do you expect to get having less than 1 digit?');
  Result := abs(aNumber);
  RangeMin := trunc(Power(10,Pred(Digits)));
  RangeMax := Pred(trunc(Power(10,Digits)));
  while Result > RangeMax do
    Result := Result div 10;
  while Result < RangeMin do
    Result := Result * 10;
end;

[WojTec]

This what I have:

Delphi-Quellcode:

function NumberDigits(ANumber: Int32; ADigits: Byte = 5): Cardinal;
var
  A: Cardinal;
begin
  A := Abs(ANumber);
  Result := Round(A * Power(10,  ADigits - Log10(A)));
end;

Result is always 1 with ADigits 0s?

Zitat:

Zitat von jfheins (Beitrag 1055748)

with fixed number of significant figures?

Exactly! I'm trying make own serial protection to stop little "crackers" :)

// Edited

@DeddyH, your function working :D

[DeddyH]

Zitat:

Zitat von Woj[I

// Edited[/I]

@DeddyH, your function working :D

Fine, but you should declare RangeMin and RangeMax as Extended to avoid wrong results due to integer overflows (did not think about this before):

Delphi-Quellcode:

function NumberToDigits(aNumber: integer; Digits: Byte = 5): Cardinal;
var RangeMin, RangeMax: Extended;
begin
  if Digits < 1 then
    raise Exception.Create('What number do you expect to get having less than 1 digit?');
  Result := abs(aNumber);
  RangeMin := Power(10,Pred(Digits));
  RangeMax := Power(10,Digits) - 1;
  while Result > RangeMax do
    Result := Result div 10;
  while Result < RangeMin do
    Result := Result * 10;
end;

[WojTec]

Maybe Int64 will be also good? and RandgeMin/Max formulas from 1st version?

[DeddyH]

Yes, I think so.

[WojTec]

I changeg Int32 to Int64 after asked, because I didn't sure range is good or not ;) In my tests all was ok, but I changed type. Thanks for help :)