8 Exception utilities

(require (planet untyped/unlib/exn))

Utilities for raising and handling exceptions.

(raise-exn id message arg ...)

Raises an exception with a default set of continuation marks. id is the identifier of the exception’s structure type transformer binding (e.g. exn or exn:fail). message and args are passed to the exception’s constructor, along with the value of current-continuation-marks.

Examples:

> (with-handlers ([exn? pretty-print])       (raise-exn exn:fail "Oops!"))

#(struct:exn:fail     "Oops!"     #<continuation-mark-set>)

> (with-handlers ([exn? pretty-print])       (raise-exn exn:fail:syntax "Oops!" (list #'a #'b #'c)))

#(struct:exn:fail:syntax     "Oops!"     #<continuation-mark-set>     (#<syntax:3:0>      #<syntax:3:0>      #<syntax:3:0>))

(reraise-exn old-exn new-exn new-message arg ...)

Raises new-exn with a message of:

  (string-append (exn-message old-exn) ": " new-message)

and the same continuation marks as old-exn. Any additional args are passed to the constructor of new-exn.

Examples:

> (with-handlers ([exn? pretty-print])       (with-handlers ([exn? (lambda (e)                               (reraise-exn e exn:fail                                 "Looks serious"))])         (raise-exn exn "Oops!")))

#(struct:exn:fail     "Looks serious: Oops!"     #<continuation-mark-set>)