Szathmáry László honlapja @ DEIK | Nim2 / removePrefix, removeSuffix

removePrefix()

removePrefix()

s = "https://python.org"

print(s.removeprefix("https://")) # python.org

print(s.removeprefix("ftp://")) # https://python.org

import std/strutils

var s = "https://python.org" # var, can be modified

s.removePrefix("https://") # change in-place

echo s # python.org ; `s` has changed!

# ---

func withoutPrefix*(s, prefix: string): string =
## Remove the given prefix. Returns a new string.
result = s
result.removePrefix(prefix)

let url = "https://python.org" # let, immutable

echo url.withoutPrefix("https://") # python.org

echo url # https://python.org ; original string

removeSuffix()

Can be done similarly to removePrefix() .

Using dup from std/sugar

See dup in std/sugar

I learned later about the dup macro, which "turns an in-place algorithm into one that works on a copy and returns this copy, without modifying its input. This macro also allows for (otherwise in-place) function chaining."

My only problem is the strange syntax when using dup:

import std/strutils
import std/sugar # dup

let
url = "https://python.org" # let, immutable
url2 = url.dup # makes a copy
# ---
naked1 = url.dup(removePrefix("https://")) # python.org
naked2 = url.dup removePrefix("https://") # python.org
naked3 = dup url: removePrefix("https://") # python.org
naked4 = url.dup: removePrefix("https://") # python.org

echo url # https://python.org
echo url2 # https://python.org

echo naked1 # python.org
echo naked2 # python.org
echo naked3 # python.org
echo naked4 # python.org

Maybe naked3 and naked4 have the best syntax. naked1 and naked2 are weird for me.