dranges.phobos_extension

struct Map (alias fun,Range) if (isInputRange!(Range));

An extended version of std.algorithm. Map , that makes it propagate the input range properties (bidirectional, etc.)

• it defines back/popBack if the input range is bidirectional.
• it defines opIndex if the range offers random-access.
• it has a length if the input range has one.
• it's infinite if the input range is infinite.
• it can be sliced if the input range can also.

Examples:

auto r = [0,1,2,3,4]; // random-access range with a length and slicing.
auto m = map!"a*a"(r);

assert(equal(retro(m), [16,9,4,1,0][])); // bidirectional range
assert(m[3] == 9); // random-access range
assert(m.length == 5); // length
assert(equal(m[1..3], [1,4][])); // slicing

auto m2 = map!"a*a"(cycle(r)); // cycle(r) is infinite
assert(isInfinite(typeof(m2))); // m2 is infinite also.
assert(!is(m2.length)); // cycle(r) doesn't have a length, so neither has m2.

Note:
map caches its front and back. So be prudent if you use callable classes/structs with an internal state (and why would you use a class as a callable if not to manage state?).

struct Filter (alias pred,Range) if (isInputRange!(Range));

An extended version of std.algorithm. Filter that defines back/popBack if the input range is bidirectional.

Example:

auto r = [0,1,2,3,4];
auto f = filter!"a%2==0"(r);
assert(equal(retro(f), [4,2,0])); // f is a bidirectional range

struct Repeat (T);

std.range. Repeat should have popBack defined.

struct Stride (R) if (isInputRange!(R));

std.range. Stride assumes a bidirectional range. This slight modification just add the necessary 'isBidirectionalRange!R' throughout the code.

struct Take (R) if (isInputRange!(R));
Take!(R) take (R)(size_t n, R input);

A corrected version of std.range.take.

/+It uses slicing when possible, to get (hopefully) a better performance.+/

The std version has problems with its back/popBack methods, they simply do not work. It seems these do work (to be thoroughly tested, though), but they depend on rather strict conditions on the input range: back/popBack needs a random-access range with a length.

struct ChainImpl (R...);

An extended version of std.range. ChainImpl .

In DMD 2.037, chain has some problems:

• opIndex doesn't deal correctly with infinite ranges
• the same for opIndexAssign

auto c = chain([0,1,2][], cycle([4,5,6][]), [7,8,9][]); // infinite range inside.
auto c7 = c[7]; // doesn't work with std.range.chain.

This version also provides some concatenation capabilities on the right with another chain (with flattening), with another range and with an element.