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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 23 |
1 files changed, 23 insertions, 0 deletions
@@ -39646,6 +39646,29 @@ notation. The reason is that a struct literal produces an object which loses information about how it was specified in the literal syntax, but those details are critically important in pattern matching. +A pattern can contain multiple occurrences of the same variable. +Except in the case when these variables occur in different branches +of an +.code @(or) +or +.code @(and) +pattern operator, those repeated variables denote one variable. +The left-most, or in the case of +.code @(let) +nesting, outermost, occurrence of the variable binds to the corresponding +element of the object. The remaining occurrences of the variable must +correspond to objects which are +.code equal +to that object, or else there is no match. +For instance, the pattern +.code "(@a @a)" +matches a list like +.code "(1 1)" +and binds a to the leftmost +.codn 1 , +and fails to match a list like +.codn "(1 2)" . + The pattern-matching notation is documented in the following sections; sections describing the pattern matching macros follow. |