Trimming (computer Programming) - Variants

Variants

Left or right trimming

The most popular variants of the trim function strip only the beginning or end of the string. Typically named ltrim and rtrim respectively, or in the case of Python: lstrip and rstrip. C# uses TrimStart and TrimEnd, and Common Lisp string-left-trim and string-right-trim. Pascal and Java do not have these variants built-in, although Object Pascal (Delphi) has TrimLeft and TrimRight functions.

Whitespace character list parameterization

Many trim functions have an optional parameter to specify a list of characters to trim, instead of the default whitespace characters. For example, PHP and Python allow this optional parameter, while Pascal and Java do not. With Common Lisp's string-trim function, the parameter (called character-bag) is required. The C++ Boost library defines space characters according to locale, as well as offering variants with a predicate parameter (a functor) to select which characters are trimmed.

Special empty string return value

An uncommon variant of trim returns a special result if no characters remain after the trim operation. For example, Apache Jakarta's StringUtils has a function called stripToNull which returns null in place of an empty string.

Space normalization

Space normalization is a related string manipulation where in addition to removing surrounding whitespace, any sequence of whitespace characters within the string is replaced with a single space. Space normalization is performed by the function named Trim in spreadsheet applications (including Excel, Calc, Gnumeric, and Google Docs), and by the normalize-space function in XSLT and XPath,

In-place trimming

While most algorithms return a new (trimmed) string, some alter the original string in-place. Notably, the Boost library allows either in-place trimming or a trimmed copy to be returned.