std.string

Formatting and character-level helpers that don’t fit the method-on-string pattern.

The core string operations — .len(), .trim(), .upper(), .split(), .contains(), .slice(), .replace(), .to_int(), .to_float(), etc. — are methods on strings. This module adds things that are awkward as methods.

Import

use std.string
use std.string.{pad_left, center}
use std.string as str

Padding

pad_left(s, width, ch) / pad_right(s, width, ch)

Pad s on the left (or right) with ch until it reaches width total characters. Already-long strings are returned unchanged. ch should be a single-character string.

use std.string.{pad_left, pad_right}
print(pad_left("42", 5, "0"))      // "00042"
print(pad_right("hi", 6, "."))     // "hi...."

center(s, width, ch)

Centre s inside width chars using ch as filler. Odd leftover space goes on the right (matches Python’s str.center).

use std.string.{center}
print(center("OK", 6, "-"))     // "--OK--"
print(center("OK", 7, "-"))     // "--OK---"

Character-level

chars(s)

Split s into an array of single-character strings, preserving order.

use std.string.{chars}
print(chars("abc"))    // ["a", "b", "c"]

reverse(s)

Reverse the character sequence. Works on ASCII and UTF-8 (iterates by code point).

use std.string.{reverse}
print(reverse("hello"))    // "olleh"

is_palindrome(s)

true when s reads the same forwards and backwards. Case-sensitive — lowercase the input first if you need case-insensitive comparison.

use std.string.{is_palindrome}
print(is_palindrome("racecar"))    // true
print(is_palindrome("Racecar"))    // false

Other helpers

count(s, needle)

Count non-overlapping occurrences of needle in s. An empty needle returns 0 (avoids the “infinite matches at every position” ambiguity).

use std.string.{count}
print(count("banana", "a"))      // 3
print(count("aaaa", "aa"))       // 2  (non-overlapping)

join(arr, sep)

Join an array of strings with sep. This is a thin wrapper around the built-in arr.join(sep) array method — it’s here so users starting from std.string don’t have to look elsewhere.

use std.string.{join}
print(join(["a", "b", "c"], "-"))    // "a-b-c"