Huffman coding comparison

[Simen kjaeraas]

bearophile <bearophileHUGS at lycos.com> wrote:

> I will keep missing array comprehensions in D. In the meantime other  
> languages have got some forms of them (but Python ones use the best  
> syntax still).

I'm now so tired of hearing this, I started writing something that
does it:

auto r = list!"2 * a" | [1,2,3,4,5] & where!"a & 1" );

Takes any kind of range, and list and where are basically map and
filter in disguise. Only thing I did was add operator overloading.

Now, granted, I have little to no experience with list comprehension,
and as such this might not be what is needed. Still, it was fun to
play around with, and I kinda like what it turned out as.



import std.algorithm;
import std.range;
import std.array;

struct listImpl( alias pred ) {
     auto opBinary( string op : "|", Range )( Range other ) {
         return map!pred(other);
     }
}

struct whereImpl( alias pred ) {
     auto opBinaryRight( string op : "&", R )( R range ) {
         return filter!pred(range);
     }
}

@property
whereImpl!pred where( alias pred )( ) {
     whereImpl!pred result;
     return result;
}

@property
listImpl!pred list( alias pred )( ) {
     listImpl!pred result;
     return result;
}

unittest {
     assert( equal( list!"2 * a" | [1,2,3,4,5] & where!"a & 1", [2,6,10] )  
);
     assert( equal( list!"2 * a" | [1,2,3], [2,4,6] ) );
}


-- 
Simen