arc> (coerce "foo" 'num) #f
arc> (coerce "foo" 'num) Error: "Can't coerce \"foo\" num"
((string? x) (case type ((sym) (string->symbol x)) ((cons) (ac-niltree (string->list x)))
((num) (apply string->number x args)) ((int) (let ((n (apply string->number x args))) (if n (iround n) (err "Can't coerce" x type)))) (else (err "Can't coerce" x type))))
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