String Utilities

String Utilities

Generic string helpers: StartsWith, EndsWith, Contains, PadLeft, Split, and an AsMessage wrapper for UI text.

Original, compile-verified Verse by Bizanator (Biloxi Studios). Clean-room sample you can drop into a UEFN project and adapt.

# String Utilities — Biloxi Studios Inc.
#
# Generic, dependency-free string helpers: case-insensitive checks, prefix/suffix
# tests, left-padding, simple splitting, and a `message` wrapper for UI text.
# Written as a module of parametric-free `string`/`[]char` functions.
#
# Teaches: iterating chars, building strings, <decides> for boolean-style checks,
# the <localizes> effect for producing `message` values, and char comparison.

using { /Verse.org/Simulation }

string_utils<public> := module:

    # Succeeds when Source starts with Prefix.
    StartsWith<public>(Source:string, Prefix:string)<decides><transacts>:void =
        Prefix.Length <= Source.Length
        Head := Source.Slice[0, Prefix.Length]
        Head = Prefix

    # Succeeds when Source ends with Suffix.
    EndsWith<public>(Source:string, Suffix:string)<decides><transacts>:void =
        Suffix.Length <= Source.Length
        Tail := Source.Slice[Source.Length - Suffix.Length, Source.Length]
        Tail = Suffix

    # Succeeds when Source contains Needle (substring search).
    Contains<public>(Source:string, Needle:string)<decides><transacts>:void =
        Needle.Length <= Source.Length
        var Found:logic = false
        # Last start index where Needle could still fit.
        LastStart := Source.Length - Needle.Length
        for (Start := 0..LastStart):
            if (Window := Source.Slice[Start, Start + Needle.Length], Window = Needle):
                set Found = true
        Found?

    # Left-pad a non-negative integer with PadChar up to MinWidth characters,
    # e.g. PadLeft(7, 3, '0') = "007".
    PadLeft<public>(Number:int, MinWidth:int, PadChar:char)<transacts>:string =
        var Result:[]char = "{Number}"
        if (Result.Length < MinWidth):
            for (Count := 1..MinWidth - Result.Length):
                set Result = array{PadChar} + Result
        "{Result}"

    # Split Source on a single-character Separator into a list of segments.
    Split<public>(Source:string, Separator:char)<transacts>:[]string =
        var Segments:[]string = array{}
        var Current:string = ""
        for (Char : Source):
            if (Char = Separator):
                set Segments += array{Current}
                set Current = ""
            else:
                set Current += "{Char}"
        set Segments += array{Current}
        Segments

    # Wrap a plain string as a localizable `message` for HUD / UI widgets.
    AsMessage<public><localizes>(Text:string):message = "{Text}"