gistfile1.md

(: normalize-histogram ((Vectorof Real) -> (Vectorof Real)))
(define (normalize-histogram hist)
  (let: ((sum (for/sum: : Real ([value : Real (in-vector hist)])
                value)))
    (for/vector: : (Vectorof Real) ([value : Real (in-vector hist)])
      (/ value sum))))

I should be able to say ((Vectorof Natural) -> (Vectorof Rational)) because the sum of natural is naturals the sum quotient of a natural and a natural is a (Positive) Rational.

I want to be able to know which branch of the case-> I'm in so that I can supply appropriate type annotations to the for macros.

For example, when normalizing a vector of numeric values, the output type should be the quotient closure of the input type. For example, a normalized vector of Naturals will be a vector of Rationals.

The heart of the issue is that the for macros require some annotation but that annotation depends on the branch of the case->, which I cannot refer to.

If you have a workaround until something is pushed to TR mainline, I'd love to hear about it!

(: normalize-histogram (case-> ((Vectorof Real) -> (Vectorof Real))
                               ((Vectorof Natural) -> (Vectorof Rational)))
(define (normalize-histogram hist)
  (let: ((sum (for/sum: : ??? ([value : ??? (in-vector hist)])
                value)))
    (for/vector: : (Vectorof ???) ([value : ??? (in-vector hist)])
      (/ value sum))))

I should be able to say ((Vectorof Natural) -> (Vectorof Rational)) because the sum of natural is naturals the sum quotient of a natural and a natural is a (Positive) Rational.