IronKernel.Strings

IronKernel.Strings

String and format utilities for IronKernel. Strings in IronKernel are CLR strings and the runtime keeps its primitive surface small; this package wraps the CLR interop in the vocabulary a Kernel program expects.

(string-split "a,b,c" ",")            ; => ("a" "b" "c")
(string-join (list "a" "b" "c") "-")  ; => "a-b-c"
(substring "hello" 1 4)               ; => "ell"
(format "{0} of {1:F1}" 2 3.0)        ; => "2 of 3.0"

Three commitments, chosen once so no caller has to think about them:

• Comparisons are ordinal. Search, prefix, suffix, and ordering compare UTF-16 units, never the current culture.
• Formatting is culture-invariant. format, number->string, and string->number read and write the invariant culture, so 3.5 renders as "3.5" on every machine.
• Half-open intervals. substring takes [start, end) like the rest of the language's ranges, not .NET's (start, length).

Use

ik add IronKernel.Strings 0.1.0

Or, from a checkout of this repository:

cd lib/IronKernel.Test && ik pack     # seed the local feed for the test DSL
cd ../IronKernel.Strings
ik test
ik pack

API

Classification

Form	Meaning
(string? x) / (char? x)	By CLR runtime type; every Kernel value answers #f.

Basics

Form	Meaning
(string-length s)	UTF-16 length.
(string-empty? s)	Length zero.
(string-ref s i)	Character at i, from zero.
(substring s start end)	The characters in [start, end).
(string-append s …)	Concatenation; no arguments give "".
(string->list s) / (list->string chars)	To and from a list of characters.

Search

Form	Meaning
(string-index-of s sub)	First index, or #f.
(string-contains? s sub)
(string-starts-with? s prefix) / (string-ends-with? s suffix)

Split and join

Form	Meaning
(string-split s sep)	Every field, empties included; sep is a non-empty string.
(string-join strings sep)
(string-lines s)	Lines, treating \r\n and \n alike; one trailing newline yields no final empty line.

Case, trimming, editing

string-upcase, string-downcase (invariant), string-trim, string-trim-start, string-trim-end, (string-replace s old new) (every occurrence, ordinal), (string-repeat s n), (string-reverse s), (string-pad-left s width [pad]), (string-pad-right s width [pad]).

Numbers

Form	Meaning
(string->number s)	The number in invariant notation, or #f. Integers stay exact (narrowed to 32-bit when they fit); a point or exponent gives an inexact. Group separators are rejected.
(number->string n [spec])	Invariant rendering; spec is a .NET format spec ("F2", "X", …).

Ordering

(string-compare a b) gives -1/0/1 ordinally; string=?, string<?, string>?, string<=?, string>=? derive from it.

Characters

char->integer, integer->char, char-digit?, char-letter?, char-whitespace?, char-upper?, char-lower?, char-upcase, char-downcase.

format

(format fmt arg …) — .NET-style holes {n} and {n:spec}, any number of arguments, {{/}} for literal braces, always the invariant culture. Implemented here rather than delegated to String.Format so the argument list is unbounded; a hole past the arguments, an empty hole, or an unbalanced brace signals an error.

Notes

• Values in format holes must be CLR-convertible (numbers, strings, booleans, CLR objects); to render Kernel structure, use show.
• The package performs no host I/O.