strreplaceold

Strreplaceold is a string manipulation function found in several programming libraries and environments. It replaces occurrences of a specified old substring with a new substring within a given input string. In most implementations, the function is non-destructive, returning a new string while leaving the original input unchanged.

The typical usage involves a signature such as strreplaceold(input, old, new, count=None, case_sensitive=True). Key parameters include input (the source string), old (the substring to replace), new (the replacement string), count (an optional limit on how many occurrences to replace), and case_sensitive (an optional flag to control case sensitivity). Behavior usually follows left-to-right, non-overlapping replacements. If the old substring is not found, the input is returned unchanged. In many implementations, passing an empty old substring raises an error to avoid undefined behavior.

Relations to other string utilities are common. Strreplaceold is often contrasted with general replace functions and with regular-expression based replacements. Some libraries offer both a non-regex version (strreplaceold) and a regex-based variant; the latter can handle patterns and complex matching, while strreplaceold focuses on fixed-string replacements. Performance characteristics vary by implementation, with most having linear or near-linear behavior relative to input length for typical cases.

Examples illustrate typical outcomes. For instance, strreplaceold("hello world", "l", "L") may yield "heLLo word" depending on case rules and replacement count. strreplaceold("abababa", "aba", "x", count=1) might produce "xbaba". Note that exact results can differ across languages and libraries; consult the specific API documentation for precise semantics and edge cases.

See also: str_replace, replace, replace_all, regex_replace.