50.9.2 Basic patterns

The simplest SRE is a literal string, which matches that string exactly.

(irregex-search "needle" "hayneedlehay")
⇒ #<match>

By default the match is case–sensitive, though we can control this either with the compiler flags or local overrides:

(irregex-search "needle" "haynEEdlehay")
⇒ #f

(irregex-search (irregex "needle" 'i) "haynEEdlehay")
⇒ #<match>

(irregex-search '(w/nocase "needle") "haynEEdlehay")
⇒ #<match>

We can use w/case to switch back to case–sensitivity inside a w/nocase or when the SRE was compiled with case-insensitive:

(irregex-search '(w/nocase "SMALL" (w/case "BIG")) "smallBIGsmall")
⇒ #<match>

(irregex-search '(w/nocase "small" (w/case "big")) "smallBIGsmall")
⇒ #f

Of course, literal strings by themselves aren’t very interesting regular expressions, so we want to be able to compose them. The most basic way to do this is with the seq operator (or its abbreviation :), which matches one or more patterns consecutively:

(irregex-search '(: "one" space "two" space "three") "one two three")
⇒ #<match>

The w/case and w/nocase operators allowed multiple SREs in a sequence; other operators that take any number of arguments (e.g. the repetition operators below) allow such implicit sequences.

To match any one of a set of patterns we use the or alternation operator:

(irregex-search '(or "eeney" "meeney" "miney") "meeney")
⇒ #<match>

(irregex-search '(or "eeney" "meeney" "miney") "moe")
⇒ #f