Associative Ranges

Abstract

Introduce Associative ranges and lazy associative ranges to phobos. A associative range is a user defined container that has all the features of a build-in associative array. A lazy associative range is a sub set of a associative with only a index operator(of any type)

Rationale

Allow abtraction of hashmaps with ranges.

Description

An associative range must have: A byKey attribute that returns an input range of keys, A byValue attribute that returns an input range of values, byKey and byValue must be align to the same Pair when iterating. An index operator that takes a key and returns a value. An in operator that takes a key and returns a value pointer(or a user defined type that acts like one) or null if it doesn’t exist.

A lazy associative range must have: An alias to the key type “KeyType” An alias to the value type “ValueType” An index operator that takes a key type and returns value.

Usage

import std.range;
struct AssociativeRange
{
    InputRange!float byKey;
    InputRange!uint byValue;
    uint opIndex(float);
    const (uint)* opBinaryRight(string op)(float) if(op=="in");
}
static assert(isAssociativeRange!AssociativeRange);
alias K=ElementKeyType!AssociativeRange;
alias V=ElementValueType!AssociativeRange;

import std.range;
struct LazyAssociativeRange
{
    alias KeyType=double;
    alias ValueType=float;
    float opIndex(double);
}
static assert(isLazyAssociativeRange!LazyAssociativeRange);
alias K=ElementKeyType!LazyAssociativeRange;
alias V=ElementValueType!LazyAssociativeRange;

Copyright

This document has been placed in the Public Domain.