Gerbil Scheme

String utilities

To use the bindings from this module:

(import :std/misc/string)

string-trim-prefix

(string-trim-prefix pfix str) -> string

  pfix := string prefix to trim
  str  := string to search in for pfix

If str starts with the given string prefix pfix, then string-trim-prefix returns the rest of str without pfix. If pfix isn't a valid prefix of str, return the entire string str instead.

Examples:

> (string-trim-prefix "date:" "date:2019-05-01")
"2019-05-01"

> (string-trim-prefix "$" "100")
"100"

> (map (cut string-trim-prefix ":std/misc/" <>)
       [":std/misc/string" ":std/misc/ports" ":std/misc/list"])
("string" "ports" "list")

string-trim-suffix

(string-trim-suffix sfix str) -> string

  sfix := string suffix to trim
  str  := string to search in for sfix

Analog to string-trim-prefix, but returns the beginning of str without the string ending sfix.

Examples:

> (string-trim-suffix ".ss" "strings.ss")
"strings"

> (map (cut string-trim-suffix ".txt" <>)
       ["README.txt" "LICENSE.txt" "CREDITS.txt"])
("README" "LICENSE" "CREDITS")

string-trim-eol

(string-trim-eol str) -> string

  str := string to trim

Trims any single end-of-line marker CR, LF or CRLF at the end of str.

Note: string-trim-eol removes only one end-of-line marker. Use (string-trim-right str (char-set #\return #\newline)) to remove all of them.

Examples:

> (string-trim-eol "foo\r")
"foo"      ; equivalent to (string-trim-suffix +cr+ "foo\r")

> (string-trim-eol "foo\n\n")
"foo\n"    ; only a single end-of-line marker is removed

string-split-prefix

(string-split-prefix pfix str) -> (values string string)

  pfix := string prefix to split after
  str  := string to search in for pfix

Split str based on given string prefix pfix, returning both the string part after the prefix as well as the prefix itself, or both the whole string and "" in case pfix isn't found in str.

string-split-prefix is similar to string-trim-prefix, but also returns the prefix as a second value.

Examples:

> (string-split-prefix "123" "123abcdef")
"abcdef"    ; suffix/rest
"123"       ; prefix

> (string-split-prefix "123" "no-numbers-here")
"no-numbers-here"
""

> (import :std/srfi/13)
> (for-each (lambda (brw)
              (let-values (((name year) (string-split-prefix (string-take brw 4) brw)))
                (displayln "initial release of " name " was " year)))
            ["2002firefox" "2003safari" "2008chrome" "2015edge"])
initial release of firefox was 2002
initial release of safari was 2003
initial release of chrome was 2008
initial release of edge was 2015

string-split-suffix

(string-split-suffix sfix str) -> (values string string)

  sfix := string suffix to split before
  str  := string to search in for sfix

Analog to string-split-prefix, but splits str based on a given string suffix sfix instead.

string-split-suffix is similar to string-trim-suffix, but also returns the suffix as a second value.

Examples:

> (string-split-suffix ".scm" "secret.scm")
"secret"    ; prefix/rest
".scm"      ; suffix

> (string-split-suffix ".scm" "secret.lisp")
"secret.lisp"
""

string-split-eol

(string-split-eol str) -> string

  str := string to split

Analog to string-trim-eol, but splits one single end-of-line marker off of str, which is then also returned as a second value.

Examples:

> (equal? +lf+ (values-ref (string-split-eol "foo\n") 1))
#t

string-subst

(string-subst str old new [count: #f]) -> string | error

  str   := string to perform changes on, won't be modified
  old   := string, what to remove
  new   := string, what to insert instead
  count := number of substitutions, optional keyword param

Substitutes/replaces string old with string new inside of str. str itself will not be modified. The procedure expects count to be a valid number (a fixnum to be precise) or #f, indicating the number of substitutions to perform, otherwise an error is signaled.

  • count #f: no limit, the default
  • count > 0: limit replacements
  • count <= 0: return input

Examples:

> (string-subst "aabbaaaaabb" "aa" "cc")
"ccbbccccabb"    ; single a remains, only replacing pairs

> (string-subst "subst;some;of;these;semicolons" ";" "#" count: 2)
"subst#some#of;these;semicolons"

string-whitespace?

(string-whitespace? str) -> boolean

  str := string to check for whitespace characters

Returns true when the string s consists only of whitespace characters.

character string name
space
\n line feed
\t horizontal tab
\r carriage return
\f form feed
\v vertical tab

Examples:

> (string-whitespace? "")
#t

> (string-whitespace? "\n \t")
#t

random-string

(random-string [len = 10]) -> string | error

  len := optional, length of the output string

random-string returns a string consisting of regex word-boundary characters ([a-zA-Z0-9_]). Throws an error if len is not a fixnum.

Examples:

> (random-string)
"5CfMyYd2Ob"

> (random-string 0)
""

str

(str . xs) -> string

  xs := values to be converted and concatenated into a string

str converts all of its arguments into a single string. When called without an argument an empty string is returned.

Examples:

> (str)
""

> (str 2.0)
"2.0"

> (str "hello" ", world")
"hello, world"

> (import :std/format :std/misc/repr)
> (defstruct point (x y))
> (def p (make-point 10 20))
> (defmethod {:pr point}
    (lambda (self port options)
      (fprintf port "(point ~a ~a)"
               (point-x self) (point-y self))))

> (str p 'abc [1 2] 3.4E+2)
"(point 10 20)abc[1 2]340.0"

str-format

(str-format v) -> string

  v := any value

str-format takes any value and returns a formatting string, which can be used by the :std/format family of procedures. Considers the :pr method from :std/misc/repr.

Examples:

> (import :std/format)
> (str-format "hello")
"~a"  ; default format

> (str-format 1.2E+2)
"~f"  ; inexact number

> (str-format (vector 1 2 3))
"~r"  ; object which implements the :pr method of :std/misc/repr

line ending variables

(define +cr+   "\r")
(define +lf+   "\n")
(define +crlf+ "\r\n")

Global line ending convenience definitions.

← Text Utilities→