diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 43 |
1 files changed, 43 insertions, 0 deletions
@@ -5428,6 +5428,47 @@ Example: Output: 1 2 3 +.SS Operator catch + +.TP +Syntax: + + (catch <try-expression> + {(<symbol> (<arg>*) <body-form>*)}*) + +.TP +Description: + +The catch operator establishes an exception catching block around +the <try-expression>. The <try-expression> is followed by zero or more +catch clauses. Each catch clause consists of a symbol which denotes +an exception type, an argument list, and zero or more body forms. + +If <try-expression> terminates normally, then the catch clauses +are ignored. The catch itself terminates, and its return value is +that of the <try-expression>. + +If <try-expression> throws an exception which is a subtype of one or more of +the type symbols given in the exception clauses, then the first (leftmost) such +clause becomes the exit point where the exception is handled. +The exception is converted into arguments for the clause, and the clause +body is executed. When the clause body terminates, the catch terminates, +and the return value of the catch is that of the clause body. + +If <try-expression> throws an exception which is not a subtype of any of +the symbols given in the clauses, then the search for an exit point for +the exception continues through the enclosing forms. The catch clauses +are not involved in the handling of that exception. + +When a clause catches an exception, the number of arguments in the catch must +match the number of elements in the exception. A catch argument list +resembles a function or lambda argument list, and may be dotted. For instance +the clause (foo (a . b)) catches an exception subtyped from foo, with one or +more elements. The first element binds to parameter a, and the rest, if any, +bind to parameter b. If there is only one element, b takes on the value nil. + +Also see: the unwind-protect operator, and the functions throw, throwf +and error. .SS Lisp Functions and Variables @@ -6585,6 +6626,8 @@ Certain object types have a custom equal function. .SS Function repeat +.SS Functions throw, throwf and error + .SH APPENDIX A: NOTES ON EXOTIC REGULAR EXPRESSIONS Users familiar with regular expressions may not be familiar with the complement |