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Language D
(Template metaprogramming)
| Date: | 07/11/06 |
| Author: | Don Clugston |
| URL: | n/a |
| Comments: | 1 |
| Info: | http://www.digitalmars.com/d |
| Score: |  (3.01 in 259 votes) |
// Displays the "99 bottles of beer" song at compile time,
// using the template metaprograming facilities of D.
// No executable is generated. No libraries are used.
// Illustrates template default values, template string value parameters,
// compile-time concatenation of constant strings, static if.
template decimaldigit(int n) {
const char [] decimaldigit = "0123456789"[n..n+1];
}
template itoa(ulong n)
{
static if ( n < 10L )
const char [] itoa = decimaldigit!(n);
else
const char [] itoa = itoa!( n / 10L ) ~ decimaldigit!( n % 10L );
}
template showHowMany(int n, char [] where, bool needcapital = false)
{
static if ( n > 1 )
const char [] showHowMany = itoa!(n) ~ " bottles of beer" ~ where ~ \n;
else static if ( n == 1 )
const char [] showHowMany = "1 bottle of beer" ~ where ~ \n;
else static if ( needcapital )
const char [] showHowMany = "No more bottles of beer" ~ where ~ \n;
else
const char [] showHowMany = "no more bottles of beer" ~ where ~ \n;
}
template beer(int maxbeers, int n = maxbeers)
{
static if ( n > 0 )
const char [] beer = showHowMany!(n, " on the wall,", true)
~ showHowMany!(n, ".")
~ "Take one down and pass it around, " \n
~ showHowMany!( n - 1 , " on the wall.")
~ \n ~ beer!(maxbeers, n - 1); // recurse for subsequent verses.
else
const char [] beer = showHowMany!(n, " on the wall,", true)
~ showHowMany!(n, ".")
~ "Go to the store and buy some more, " \n
~ showHowMany!( maxbeers, " on the wall.");
}
pragma(msg, beer!(99));
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Alternative Versions
| Version | Author | Date | Comments | Rate |
|---|---|---|---|---|
| 1 | Stewart Gordon | 05/31/05 | 4 | |
| D feuture's galore | Fredrik Olsson | 10/09/05 | 2 | |
| Fiber "Ring" | Bryan Knowles | 11/17/10 | 0 | |
| Div Operator Edition | badmadevil | 02/29/08 | 0 | |
| 5 | Philipp Winterberg | 04/20/05 | 7 | |
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