List comprehensions: Difference between revisions

List comprehension is done in the standard library with the collect() macro (which uses for-loop macros) from the sugar package:

<lang nim>import sugar, math

let n = 20

let triplets = collect(newSeq):

for x in 1..n:

for y in x..n:

for z in y..n:

if x^2 + y^2 == z^2:

(x,y,z)

echo triplets</lang>

Output:

<pre>@[(3, 4, 5), (5, 12, 13), (6, 8, 10), (8, 15, 17), (9, 12, 15), (12, 16, 20)]</pre>

A special syntax for list comprehensions in Nim can be implemented thanks to the strong metaprogramming capabilities: