string=?, string<?, string>?, string<=?, string>=? - string comparison


(import (rnrs))                     ;R6RS
(import (rnrs base))                ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS


(string=? string1 string2 string3 ...)
(string<? string1 string2 string3 ...)
(string>? string1 string2 string3 ...)
(string<=? string1 string2 string3 ...)
(string>=? string1 string2 string3 ...)


The string=? procedure returns #t if all the strings are the same length and contain exactly the same characters in the same positions, otherwise returns #f.

The ordering procedures return #t if their arguments are (respectively): monotonically increasing, monotonically decreasing, monotonically nondecreasing, or monotonically nonincreasing. The behavior of the ordering procedures is different in R6RS and R7RS:

These procedures are the lexicographic extensions to strings of the corresponding orderings on characters. For example, string<? is the lexicographic ordering on strings induced by the ordering char<? on characters. If two strings differ in length but are the same up to the length of the shorter string, the shorter string is considered to be lexicographically less than the longer string.
The ordering procedures compare strings in an implementation-defined way. They may work the same as in R6RS, or they could use some other ordering.

These predicates are required to be transitive. In all cases, a pair of strings must satisfy exactly one of string<?, string=?, and string>?, and must satisfy string<=? if and only if they do not satisfy string>? and string>=? if and only if they do not satisfy string<?.


These procedures return a single value; a boolean.


(string=? "Straße" "Strasse")  =>  #f
(string<? "z" "ß")             =>  #t
(string<? "z" "zz")            =>  #t
(string<? "z" "Z")             =>  #f


The basic idea of these procedures is the same in all RnRS revisions. However, there are some differences.

R5RS and earlier reports only provided two-argument variants.

R6RS implementations all work the same.

R7RS implementations may lack support for some characters. The order is also implementation-defined, with lexicographical ordering only being one option.


This procedure can raise exceptions with the following condition types:
&assertion (R6RS)
The wrong number of arguments was passed or an argument was outside its domain.
The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically.


char<?(3scm), string-ci=?(3scm), equal?(3scm)


R4RS, IEEE Scheme, R5RS, R6RS, R7RS


These procedures first appeared in R2RS. MacLisp had the samepnamep and alphalessp procedures that took two arguments and worked on both symbols and strings.


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Markup created by unroff 1.0sc,    March 04, 2023.