23 String utilities

(require (planet untyped/unlib/string))

Useful string utilities. Compatible with PLT 4 languages.

(string+false? item) → boolean?

item : any

Returns #t if item is a string and #f otherwise.

(ensure-string item) → any

item : any

Converts bytes arguments to strings: passes all other arguments straight through.

(string-length/c max) → flat-contract?

max : natural

(string-length/c min max) → flat-contract?

min : natural

max : natural

Creates a contract that recognises strings with a length within the specified inclusive bounds.

(string-delimit   items             delimiter            [ #:prefix prefix             #:suffix suffix])   →   string?

items : (listof string?)

delimiter : string?

prefix : (U string? #f) = #f

suffix : (U string? #f) = #f

Similar to string-join from SRFI 13, except that the optional #:prefix and #:suffix arguments can be provided to add a prefix or suffix string.

Examples:

> (string-delimit '("1" "2" "3") ",")

"1,2,3"

> (string-delimit '("1" "2" "3") "," #:prefix "[")

"[1,2,3"

> (string-delimit '("1" "2" "3") "," #:suffix "]")

"1,2,3]"

> (string-delimit '("1" "2" "3") "," #:prefix "[" #:suffix "]")

"[1,2,3]"

> (string-delimit '("1" "2" "3") "," #:prefix #f #:suffix #f)

"1,2,3"

(string-ellipsify str [max-length ellipsis]) → string?

str : string?

max-length : natural? = 20

ellipsis : string? = "..."

Returns a shortened version of str that is never longer than max-length. If necessary, str is truncated and ellipsis is appended.

Examples:

> (string-ellipsify      "The quick brown fox jumped over the lazy dog.")

"The quick brown f..."

> (string-ellipsify      "The quick brown fox.")

"The quick brown fox."

(number+false->string+false num) → (U string? #f)

num : (U number? #f)

A version of number->string that accepts and passes through #f.

(string+false->number+false str) → (U number? #f)

str : (U string? #f)

A version of string->number that accepts and passes through #f.

(string+false->symbol+false str) → (U symbol? #f)

str : (U string? #f)

A version of string->symbol that accepts and passes through #f.

(symbol+false->string+false sym) → (U string? #f)

sym : (U symbol? #f)

A version of symbol->string that accepts and passes through #f.