pegged.examples.pattern

This module is an attempt at introducing pattern-matching in D.

Pattern matching is a type- or value-matching present in functional languages like ML or Haskell.

The goal here is to obtain code like:

1 Pattern!"[ a, b, ... ]" p1; // match any range with at least two elements
2                             // the rest being discarded.
3 
4 auto m1 = p1([0,1,2,3,4]); // match and associate 'a' and 'b' with O and 1.
5 assert(m1.a == 0 && m1.b == 1);
6 auto m2 = p1("abc");
7 assert(m2.a = 'a' && m2.b == 'b');
8 auto m3 = p1(tuple("abc",0)); // not a range, the pattern fails
9 assert(m3 == matchFailure; // predefined constant
10 
11 Pattern!"Tuple!(.,.) t" p2; // match any std.typecons.Tuple with two elements, of any type
12 auto m4 = p2(tuple("abc",0));
13 assert(m4.t = tuple("abc",0); // only the global pattern is named, and hence captured
14 assert(p2(tuple("abc")) == matchFailure); // only one member -> failure
15 assert(p2(tuple("abc",0,1)) == matchFailure); // three members -> failure (the pattern has no trailing ...
16 
17 Pattern!" . { int, double, double }" p3; // match any aggregate (struct, class)
18                                          // with three members being int,double and double, in that order.

Don't salivate, it's not implemented yet.