On Sat, Jan 7, 2017 at 4:49 AM, John Cowan <xxxxxx@ccil.org> wrote:

On Wed, Jan 4, 2017 at 1:46 AM, Alex Shinn <xxxxxx@gmail.com> wrote:

2. it's quadratic in code size for optional argument handling

If naively implemented, yes.

I'm not talking about implementation, I'm talking about

usage (pre-expanded code). Consider:

(define foo

(opt-lambda ((a 1) (b 2) (c 3) (d 4))

...))

versus

(define foo

(case-lambda

(() (foo 1 2 3 4))

((a) (foo a 2 3 4))

((a b) (foo a b 3 4))

((a b c) (foo a b c 4))

((a b c d) ...)))

This is actually unacceptable because it duplicates the

defaults multiple times. You should instead write it as

(define foo

(case-lambda

(() (foo 1))

((a) (foo a 2))

((a b) (foo a b 3))

((a b c) (foo a b c 4))

((a b c d) ...)))

and hope that the premature optimizations have handled

this so it doesn't require four extra recursions for (foo).

Even then, you're requiring the programmer to write a

number of clauses linear in the number of parameters,

while the size of the clauses is quadratic!

Alex