2.3 mischief/error: Reporting Errors
| (require mischief/error) | package: mischief |
syntax
Use in code that should be impossible to reach. Reports an error
message including its source location. If applied as a function to arguments,
those are included in the error message.
Examples:
> (define (sum xs) (match xs [(list x) x] [(cons x xs) (+ x (sum xs))] [_ impossible])) > (sum (list 1 2 3 4)) 10
> (sum (list)) impossible: internal error at eval:1.0; should never be
called
> (define (prod xs) (match xs [(list x) x] [(cons x xs) (* x (prod xs))] [_ (impossible xs)])) > (prod (list 1 2 3 4)) 24
> (prod (list)) impossible: internal error at eval:4.0; should never be
called: (impossible '())
procedure
(format-application proc arg ... #:<any-keyword> kw-arg ...) → string? proc : any/c arg : any/c kw-arg : any/c
Produces a string representing the application of proc to the supplied
set of positional and keyword arguments.
Example:
> (format-application sort '(cat hat sat bat) string<? #:key symbol->string) "(sort #:key #<procedure:symbol->string> '(cat hat sat bat) #<procedure:string<?>)"
procedure
(format-values arg ...) → string?
arg : any/c
Produces a string representing an expression that returns the args as
multiple values, or just the singular arg if only one is given.
Examples:
> (format-values 1 2 3) "(values 1 2 3)"
> (format-values 1 2) "(values 1 2)"
> (format-values 1) "1"
> (format-values) "(values)"
procedure
(format-exception x) → string?
x : any/c
Produces a string representing an expression that raises x as
an exception.
Examples:
> (format-exception (exn:fail:contract "Epic fail!" (current-continuation-marks))) "(error \"Epic fail!\")"
> (format-exception 'not-an-exception) "(raise 'not-an-exception)"