Hi everyone,
I'm implementing an operation in Typed Racket to find the maximum element of a
vector (if this already exists and I missed it, I'd love a pointer to
it!). Unfortunately, it seems that my attempt to save a couple CPU cycles
results in a bunch of nasty type errors.
In the code below, vector-max type checks fine but vector-max2 gives me the
nasty type errors below. Can anyone shed some light on what I'm doing
incorrectly?
Thanks!
. Type Checker: untyped identifier normalise-inputs imported from module
<for.rkt> in: (define (vector-max2 vec) (for/fold: : Real ((biggest ((inst
vector-ref Real) vec 0))) ((element (in-vector vec 1))) (max biggest
element)))
. Type Checker: Expected VectorTop, but got Any in: (define (vector-max2 vec)
(for/fold: : Real ((biggest ((inst vector-ref Real) vec 0))) ((element
(in-vector vec 1))) (max biggest element)))
. Type Checker: Expression should produce 4 values, but produces 1 values of
types Nothing in: (define (vector-max2 vec) (for/fold: : Real ((biggest ((inst
vector-ref Real) vec 0))) ((element (in-vector vec 1))) (max biggest
element)))
. Type Checker: Expected Integer, but got Any in: (for/fold: : Real ((biggest
((inst vector-ref Real) vec 0))) ((element (in-vector vec 1))) (max biggest
element))
. Type Checker: Expected Integer, but got Any in: (for/fold: : Real ((biggest
((inst vector-ref Real) vec 0))) ((element (in-vector vec 1))) (max biggest
element))
. Type Checker: Expected Integer, but got Any in: (for/fold: : Real ((biggest
((inst vector-ref Real) vec 0))) ((element (in-vector vec 1))) (max biggest
element))
The code in question:
#lang typed/racket
(: vector-max ((Vectorof Real) -> Real))
(define (vector-max vec)
(for/fold: : Real ([biggest ((inst vector-ref Real) vec 0)])
([element vec])
(max biggest element)))
(: vector-max2 ((Vectorof Real) -> Real))
(define (vector-max2 vec)
(for/fold: : Real ([biggest ((inst vector-ref Real) vec 0)])
([element (in-vector vec 1)])
(max biggest element)))
--
Dan King
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