CODEWITHSUNDEEP
nim-lang
Alex Craft
Alex Craft

Reputation: 15336

How to unpack tuple in arguments with sugar in Nim?

Is it possible to unpack tuple in arguments?

import sugar, sequtils

echo @[(1, 1), (2, 2)].filter((point) => point[0] > 1) # Works  
echo @[(1, 1), (2, 2)].filter(((x, y)) => x > 1)       # Error

Upvotes: 2

Views: 551

Answers (1)

pietroppeter
pietroppeter

Reputation: 1473

The sugar macro => can sort of unpack tuple arguments, as the following example (taken from docs) shows:

proc passTwoAndTwo(f: (int, int) -> bool): bool =
  f(2, 2)

echo passTwoAndTwo((x, y) => x > 1) # true

Sort of, since it is actually treating x and y as two different arguments, not as element of a tuple.

In fact, the problem is the syntax ((x, y)) => x > 1 which is not supported by => (you can check that by running it with a discard in front).

I am not sure how easy or reasonable would be to require => to support the special case of passing a tuple.

For your use cases the following two lines are working alternatives once you have a Point type defined:

echo @[(1, 1).Point, (2, 2)].filter(point => point.x > 1)
echo @[(1, 1), (2, 2)].filterIt(it.Point.x > 1)

Upvotes: 3

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