diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim index 479acc0753..85ba802611 100644 --- a/lib/pure/strutils.nim +++ b/lib/pure/strutils.nim @@ -2281,18 +2281,31 @@ func replaceWord*(s, sub: string, by = ""): string {.rtl, add result, substr(s, i) func multiReplace*(s: string, replacements: varargs[(string, string)]): string = - ## Same as replace, but specialized for doing multiple replacements in a single - ## pass through the input string. + ## Same as `replace<#replace,string,string,string>`_, but specialized for + ## doing multiple replacements in a single pass through the input string. ## - ## `multiReplace` performs all replacements in a single pass, this means it - ## can be used to swap the occurrences of "a" and "b", for instance. + ## `multiReplace` scans the input string from left to right and replaces the + ## matching substrings in the same order as passed in the argument list. + ## + ## The implications of the order of scanning the string and matching the + ## replacements: + ## - In case of multiple matches at a given position, the earliest + ## replacement is applied. + ## - Overlaps are not handled. After performing a replacement, the scan + ## continues from the character after the matched substring. If the + ## resulting string then contains a possible match starting in a newly + ## placed substring, the additional replacement is not performed. ## ## If the resulting string is not longer than the original input string, ## only a single memory allocation is required. ## - ## Replacements are done left to right in the string. If at a given position - ## multiple replacements match, earlier replacements are preferred over - ## later replacements in the argument list. + runnableExamples: + # Swapping occurrences of 'a' and 'b': + doAssert multireplace("abba", [("a", "b"), ("b", "a")]) == "baab" + + # The second replacement ("ab") is matched and performed first, the scan then + # continues from 'c', so the "bc" replacement is never matched and thus skipped. + doAssert multireplace("abc", [("bc", "x"), ("ab", "_b")]) == "_bc" result = newStringOfCap(s.len) var i = 0 var fastChk: set[char] = {}