10:05 <Putonlalla> My procedure or macro is given an association list as an argument. How can I pass it into `parameterize` to serve as bindings? I can't find any way to control evaluation or macro expansion order to do this in R5RS.

10:13 <Putonlalla> The obvious ``(define (with-instance inst proc) (eval `(parameterize ,inst (proc))))`` doesn't work.

14:43 <samth> Putonlalla: write a recursive function

14:44 <samth> Putonlalla: `(define (with-instance l p) (if (null? l) (p) (parameterize ([(caar l) (cdar l)]) (with-instance (cdr l) p))))`

14:46 <Putonlalla> If I allow myself to `(#%require (prefix base: racket/base))`, then I can do ``(base:define-namespace-anchor anchor) (define (with-instance-thunk inst thunk) (eval `(parameterize ,inst (,thunk)) (base:namespace-anchor->namespace anchor)))``.

14:48 <Putonlalla> Your suggestion fails with `extend-parameterization: contract violation`.

14:52 <samth> Putonlalla: what's the rest of that error message?

14:52 <samth> doing `eval` is almost certainly a terrible idea

14:54 <Putonlalla> The rest says `expected: parameter?` but `given: fmap-method`. I have previously run `(define fmap-method (make-parameter 'unimplemented-method))`.

14:56 <Putonlalla> I'm exploring an alternative way to express type classes; one, that also supports constraints/dependent types.

14:58 <Putonlalla> It "works", but relies on Racket's `eval`, as you can see.

14:58 <samth> Putonlalla: are you passing in the symbol `'fmap-method` rather than the value `fmap-method`?

15:04 <Putonlalla> This is what I have. https://pastebin.com/bzNXYhT4

15:07 <Putonlalla> That's the minimized version, anyway.

15:07 <samth> Putonlalla: you need an unquote before `fmap-method` in `list-functor`

15:22 <Putonlalla> Now it throws some other error. I'll have to investigate later.

15:24 <samth> Putonlalla: your alist has an extra cons, so you can either change `cdar` to `cadar` or add a ` . ` in the quoted alist

15:26 <Putonlalla> Thanks, I'll have to look into it.

15:27 <samth> as an example of what doesn't work with `eval`, try putting a `(let () ...)` around the definition and use of `list-functor`