This page has been superceded by a wiki version of this example: CurrencyUsingWithExample

/*

    Title:   Currency with Operator Overloading (using "with")

    File:    with.d

    Author:  J C Calvarese, http://jcc_7.tripod.com/d/

    Date:    2004/01/03

    Licence: Public domain





    TEST version: outputs more information to the console during run.

*/





import std.string;

import std.math;







char[] leadingZeros(byte num, byte digits)

/* by J C Calvarese, also in locales2.d */

{ 

    char[] buffer;

    byte diff;

    

    buffer = toString(num);

    if (buffer.length < digits) 

    {

        diff = digits - buffer.length;

        for(int i=0; i < diff; i++)

          buffer = "0" ~ buffer;

    } 

    return buffer;

}







char[] toStringFromDouble(double d)

{

    return toStringFromDouble(d, 2); /* defaults to 2 decimal places */ 

}



char[] toStringFromDouble(double d, int decPlaces)

{

    return toStringFromDouble(d, decPlaces, "."); /* separator defaults to period */ 

}



char[] toStringFromDouble(double i, int decPlaces, char[] sep)

{  

    int whole;

    int dec;

    double decPart;

    

    whole = cast(int) i;

    version(TEST) printf("whole: %d\n", whole);



    decPart = (i - whole) * pow(cast(real) 10, cast(uint) decPlaces);

    version(TEST) printf("decPart: %lf\n", decPart);

    

    dec = cast(int) (decPart);

    version(TEST) printf("dec: %d\n", dec);

    return toString(i) ~ sep ~ leadingZeros(dec, decPlaces);

}







class Currency

{   

    /* Read property ("get-ter") */

    double value() {return intValue;}

    

    /* Write property ("set-ter") */

    double value(double v) {return intValue = v;}



    

    this(double v)

    {

        version(TEST) printf("An instance of the Currency object is created.\n\n");

        intValue = v;

        intSeparator = ".";

        intDecPlaces = 2;

    }

    

    this()

    {

        this(0);

    }

    

    char[] toString() { return toStringFromDouble(intValue, intDecPlaces, intSeparator);}







    /* operator overloading */



    Currency opAdd(Currency m, Currency n)

    {  

        Currency t;

        t.value = m.value + n.value;

        return t;

    }



    Currency opAddAssign(Currency m)

    {  

        intValue += m.value;

        return this;

    }





    private 

    {

        double intValue;

        double intDecPlaces;

        char[] intSeparator; /* decimal, period (U.S.), comma (Some non-U.S. locations) */

    }

}







void main()

{ 

    Currency c; // = new Currency();  

    with(c = new Currency())

    { 

        printf("\n\n\t\t\t\t\t\t%.*s\n", toString);

    

        printf("Change the value\t\t\t\t");

        value = 100.75;

        printf("%.*s\n", toString);

    }

    

    Currency c2;    

    with(c2 = new Currency(26.12))

    { 

        printf("\t\t\t\t\t\t%.*s\n", toString);

    

        printf("Change the value\t\t\t\t");

        value = 6.25;

        printf("%.*s\n", toString);

    

        printf("Change the value (operator overloading)\t\t");

        c2 += c; /* requires operator overloading */

        printf("%.*s\n\n", toString);

    }

}