Tips for golfing in Nim

Question

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.

Answer 1

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]

Answer 2

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.

Answer 3

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

Answer 4

Use on and off as a boolean value

on / off are aliases for true / false.

Answer 5

Use ; to end statements

Oftentimes, a lot of Nim bytes come from the mandatory indentation of two spaces. This can sometimes be avoided by utilizing ; to break statements. For example (a bit contrived, but nevertheless effectively demonstrating the idea):

while 1>0:echo "Hello";echo"World"

Answer 6

1>0 for true and 0>1 for false

In Nim, there is no implicit conversion of int->bool or bool->int. It is thus advantageous for golfing to use 1>0 or 0>1 to get the values for true and false, as one might use 1/0 in C. This can help with, for example, the creation of infinite loops.