chickadee » srfi-135 » subtextual

These procedures return a text containing the characters of text or textual beginning with index start (inclusive) and ending with index end (exclusive).

If textual is a string, then that string does not share any storage with the result, so subsequent mutation of that string will not affect the text returned by subtextual. When the first argument is a text, as is required by subtext, the implementation returns a result that shares storage with that text. These procedures just return their first argument when that argument is a text, start is 0, and end is the length of that text.