= Formating Numbers =

''Part of'' TutorialIntermediate

== Description ==

This function takes a number as a char array and inserts commas in the right places; "1000" becomes "1,000", etc.; for numbers smaller than that, it just returns the original.

Some overloads were added so that some integers can be converted, too. Negative values and floating-point numbers (which aren't handled yet) would require more code.

== Example ==
{{{
#!d
import std.string; /* for StringException */


string formatNumber(int i)  { return formatNumber(toString(i)); }
string formatNumber(long i) { return formatNumber(toString(i)); }
string formatNumber(bool i)  { return formatNumber(toString(i)); }


string formatNumber(string n)
{
    char[] number=n.dup;
    for(int i=n.length-3; i>=1; i-=3)
    {
        if(!std.ctype.isdigit(number[i]))
            throw new StringException("expected digits:"~n);
        else
            number=number[0..i]~","~number[i..$];
    }
    return number;
}


version(example) import std.stdio; /* for writefln (for un) */

unittest
{
    version(example) writefln("Running unittest...");
    assert(formatNumber("100")=="100");
    assert(formatNumber("1000")=="1,000");
    assert(formatNumber("10000000")=="10,000,000");
    version(example) writefln("unittest Passed!");
}


version(example) void main() /* Usage Example */
{
    writefln(formatNumber(1)); 
    writefln(formatNumber(12));
    writefln(formatNumber(123)); 
    writefln(formatNumber(1234)); 
    writefln(formatNumber(12345)); 
    writefln(formatNumber(123456)); 
    writefln(formatNumber(1234567)); 
    writefln(formatNumber(12345678)); 
    writefln(formatNumber(123456789)); 
    writefln(formatNumber(1234567890)); 
}
}}}

== Compilation Tips ==

 * Compile with -version=example to run example.
 * Compile with -unittest to run unittests when the program is run.

== Batch File ==

{{{
@echo off
dmd FormatNumberExample.d -c
dmd FormatNumberExample.d -unittest -version=example
dmd FormatNumberExample.d -version=example
FormatNumberExample.exe
pause
erase FormatNumberExample.obj
erase FormatNumberExample.map
erase FormatNumberExample.exe
}}}

== Console Output ==

{{{
c:\dmd\bin\..\..\dm\bin\link.exe string,,,user32+kernel32/noi;
c:\dmd\bin\..\..\dm\bin\link.exe string,,,user32+kernel32/noi;
1
12
123
1,234
12,345
123,456
1,234,567
12,345,678
123,456,789
1,234,567,890
Press any key to continue . . .
}}}

== Source ==

 * Based on [http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D&artnum=32149 digitalmars.D/32149] by Ameer Armaly.
 * Corrected to get unittest to pass by J C Calvarese.

== Testing ==

Tested with Digital Mars D Compiler v0.143 on Windows 2000.