Alternation constructs modify a regular expression to enable either/or matching. These constructs include the language elements listed in table 1.
Alternation construct |
Description |
| |
Matches any one element separated by the vertical bar (|) character. |
(?( expression )yes | no ) |
Matches yes if the regular expression pattern designated by expression matches; otherwise, matches the optional no part.expression is interpreted as a zero-width assertion. |
(?( name ) yes |no ) |
Matches yes if name, a named or numbered capturing group, has a match; otherwise, matches the optional no. |
Table 1: Alternation constructs
Pattern |
Matches |
th(e|is|at) |
"the", "this" in "this is the day. " |
(?(A)A\d{2}\b|\b\d{3}\b) |
"A10", "910" in "A10 C103 910" |
(?<quoted>")?(?(quoted).+?"|\S+\s) |
Dogs.jpg, "Yiska playing.jpg" in "Dogs.jpg "Yiska playing.jpg"" |
Table 2: Examples for alternation constructs
