try-catch-finally🔗 i

Alex Knauth

(require try-catch-finally ) package: try-catch-finally-lib

A macro for catching exceptions and running teardown operations.

syntax
( try body...+catch-clause...maybe-finally-clause)

catch-clause = (catch pred-expr=> handler-expr)
| (catch (pred-exprid)handler-body...+)
| (catch (id)handler-body...+)
| (catch _ handler-body...+)

maybe-finally-clause =
| (finally post-body...+)

After evaluating the pred-exprs and handler-exprs, try evaluates the bodys with the new exception handlers, and then evaluates the post-bodys even if execution exits the bodys through an exception or continuation.

Examples:

> (try
(raise-syntax-error #f"a syntax error")
(catch (exn:fail:syntax? e)
(displayln "got a syntax error")))

got a syntax error

> (try
(raise-syntax-error #f"a syntax error")
(catch (exn:fail:syntax? e)
(displayln "got a syntax error"))
(catch (exn:fail? e)
(displayln "fallback clause")))

got a syntax error

> (try
(displayln "at")
(finally (displayln "out")))

at

out

> (let/cc up
(try
(displayln "at before")
(up(void ))
(displayln "at after")
(finally (displayln "out"))))

at before

out

syntax
( catch pred-expr=> handler-expr)
(catch (pred-exprid)handler-body...+)
(catch (id)handler-body...+)
(catch _ handler-body...+)

syntax
( finally post-body...+)

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