8 Text Representations

(require (planet cce/scheme:4:1/text))

This module provides tools for manipulating and converting textual data.

8.1 Contracts and Predicates

text/c : flat-contract?

(text? v) → boolean?   v : any/c

This contract and predicate recognize text values: strings, byte strings, symbols, and keywords, as well as syntax objects containing them.

Examples:

> (text? "text")

#t

> (text? #"text")

#t

> (text? 'text)

#t

> (text? '#:text)

#t

> (text? #'"text")

#t

> (text? #'#"text")

#t

> (text? #'text)

#t

> (text? #'#:text)

#t

> (text? '(not text))

#f

(string-literal? v) → boolean?   v : any/c

(bytes-literal? v) → boolean?   v : any/c

(keyword-literal? v) → boolean?   v : any/c

These predicates recognize specific text types stored in syntax objects.

Examples:

> (string-literal? #'"literal")

#t

> (string-literal? "not literal")

#f

> (bytes-literal? #'#"literal")

#t

> (bytes-literal? #"not literal")

#f

> (keyword-literal? #'#:literal)

#t

> (keyword-literal? '#:not-literal)

#f

8.2 Text Conversions

(text->string text ...) → string?   text : text/c

(text->bytes text ...) → bytes?   text : text/c

(text->symbol text ...) → symbol?   text : text/c

(text->keyword text ...) → keyword?   text : text/c

These functions convert text values to specific types, retaining their textual content and concatenating text when necessary.

Examples:

> (text->string #"concat" #'enate)

"concatenate"

> (text->bytes 'concat #'#:enate)

#"concatenate"

> (text->symbol '#:concat #'"enate")

concatenate

> (text->keyword "concat" #'#"enate")

#:concatenate

(text->string-literal text ... [#:stx stx]) → string-literal?   text : text/c   stx : (or/c syntax? false/c) = #f

(text->bytes-literal text ... [#:stx stx]) → bytes-literal?   text : text/c   stx : (or/c syntax? false/c) = #f

(text->identifier text ... [#:stx stx]) → identifier?   text : text/c   stx : (or/c syntax? false/c) = #f

(text->keyword-literal text ... [#:stx stx]) → keyword-literal?   text : text/c   stx : (or/c syntax? false/c) = #f

These functions convert text values to specific syntax object types, retaining their textual value, concatenating text when necessary, and deriving syntax object properties from the stx argument.

Examples:

(define (show stx) (values stx (syntax-e stx)))

> (show (text->string-literal #"concat" #'enate))

#<syntax>

"concatenate"

> (show (text->bytes-literal 'concat #'#:enate))

#<syntax>

#"concatenate"

> (show (text->identifier '#:concatenate #:stx #'props))

#<syntax:4:0>

concatenate

> (show (text->keyword-literal "concatenate" #:stx #'props))

#<syntax:5:0>

#:concatenate

8.3 Text Concatenation

(text-append  [ #:before before             #:between between             #:after after]             text ...)   →   text/c

before : string? = ""

between : string? = ""

after : string? = ""

text : text/c

Produces a text value (of arbitrary type) concatenating each text input. Multiple inputs are joined with between, and given prefix before and suffix after.

Examples:

> (text-append #'one '- #'two)

"one-two"

> (text-append #:before "(" #:between ", " #:after ")")

"()"

> (text-append #:before "(" #:between ", " #:after ")" "Tom")

"(Tom)"

> (text-append #:before "(" #:between ", " #:after ")"                  "Tom" "Dick" "Harry")

"(Tom, Dick, Harry)"

8.4 Text Comparisons

(text=? one two) → boolean?   one : text/c   two : text/c

(text<? one two) → boolean?   one : text/c   two : text/c

(text<=? one two) → boolean?   one : text/c   two : text/c

(text>? one two) → boolean?   one : text/c   two : text/c

(text>=? one two) → boolean?   one : text/c   two : text/c

These predicates compare the character content of two text values. They are equivalent to:

(text=? one two) = (string=? (text->string one) (text->string two))

(text<? one two) = (string<? (text->string one) (text->string two))

(text<=? one two) = (string<=? (text->string one) (text->string two))

(text>? one two) = (string>? (text->string one) (text->string two))

(text>=? one two) = (string>=? (text->string one) (text->string two))

Examples:

> (text=? #"x" #'y)

#f

> (text<? #"x" #'y)

#t

> (text<=? #"x" #'y)

#t

> (text>? #"x" #'y)

#f

> (text>=? #"x" #'y)

#f