List Comprehension

rascal-0.40.17

Synopsis

A list comprehension generates a list value.

Syntax

[ Exp₁, Exp₂, ... | Gen₁, Gen₂, ... ]

Types

Exp₁	Exp₂	...	[ Exp₁, Exp₂, ... \| Gen₁, Gen₂, ... ]
T₁	T₂	...	list[ lub( T₁, T₂, ... ) ]

Description

A list comprehension consists of a number of contributing expressions Exp₁, Exp₂, ... and a number of generators Gen₁, Gen₂, Gen₃, ... that are evaluated as described in Comprehensions.

Examples

Computing a list of squares of the numbers from 0 to 10 that are divisible by 3:

rascal>[n * n | int n <- [0 .. 10], n % 3 == 0];
list[int]: [0,9,36,81]

But we can also include the relevant n in the resulting list:

rascal>[n, n * n | int n <- [0 .. 10], n % 3 == 0];
list[int]: [0,0,3,9,6,36,9,81]