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What general tips do you have for golfing in Nim? I'm looking for ideas which can be applied to code-golf problems and which are also at least somewhat specific to Nim (e.g. "remove comments" is not an answer).

Please post one tip per answer.

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Use the future module

The future module contains two main byte-saving features: lambdas and list comprehensions. Lambdas are extremely useful.

For example, this:

proc f(s:any):any=s&", world!"

can be shortened to this:

import future
s=>s&", world!"

which saves a byte. Note, however, that lambdas can't be used outside of a parameter list -- so to test your code, you'll have to do something like this:

import future
proc test(f: string -> string) = echo f "Hello"
test(s=>s&", world!")

As well, list comprehensions can be used with the future module. For example, this code prints a seq (@[...]) of all squares less than 100 divisible by 4:

import future
echo lc[x*x|(x<-1..9,x*x mod 4==0),int]
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  • \$\begingroup\$ For a fairer comparison it should be noted that you can sometimes use any instead of string (I'm assuming you chose the longest type name), but this still saves regardless. \$\endgroup\$ – Sp3000 Nov 26 '16 at 23:43
  • \$\begingroup\$ @Sp3000 I didn't know you could use any, thanks for the tip! You should post that as an answer. \$\endgroup\$ – Copper Nov 27 '16 at 11:55
  • \$\begingroup\$ For an even better comparison, you can do proc(s:any):any=s&", world!", dropping the <space>f for an anonymous proc \$\endgroup\$ – Sp3000 Dec 20 '16 at 9:57
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Flexible call syntax

Nim is pretty flexible when it comes to function call syntax. For example, here are some ways to call a function with one argument:

ord(c)
ord c
c.ord

And ways to call a function with two arguments:

max(a,b)
a.max(b)
a.max b

Choose the golfiest version that works right for your situation, especially regarding precedence. For example, compare:

abs(n)+2
n.abs+2
(abs n)+2

As opposed to:

abs(n+2)
(n+2).abs
abs n+2
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  • \$\begingroup\$ Note that max a,b even works (sometimes). \$\endgroup\$ – Copper Nov 26 '16 at 18:49
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Unsigned operators

When working with nonnegative integers, sometimes it's better to use unsigned operators. Specifically, if possible, use /% and %% instead of div and mod.

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