Example of how nim siloes side-effecting code

side-effects.nim

import httpClient
import strutils

func protocol(url: string): bool = ## ok, pure function
  return "http://" in url

func get(url: string): string = ## side-effects.nim(7, 6) Error: 'get' can have side effects
  if protocol url:
    return newHttpClient().getContent(url)
    
proc get(url: string): string = ## This now works. `get()` must be defined as a `proc` as it causes side effects
  if protocol url:
    return newHttpClient().getContent(url)

$ nim c side-effects.nim
side-effects.nim(7, 6) Error: 'get' can have side effects