Find with multiple predicates & quote-define

[mwgkgk]

Trying to use find like this:

(1 'hello 3) ('hello ==) find

Fails with [==]: Two non-symbol values of similar type are required on the stack. (Which is probably a usecase in it's own - to have a scheme-like hierarchy of eq? eqv? equal? with more-permissive and less-permissive variants).

Trying to safeguard this with quotation?, I cannot figure out a way to apply multiple predicates, because quotation? just executes and puts it's result on the stack, and we have nothing left to check against. Trying to quote-define the argument for reuse like this:

(1 'hello 3) (#item item quotation?) find

Results in [bind]: Attempting to bind undefined symbol: item. In general I couldn't get quote-define to work even in the form it's seen in tutorial:

(1 2 3 4 5) #my-list

Using the github version of Min.

Thank you for your time <3

[mwgkgk]

Was able to work around it with dup:

 (1 'hello 3) (dup quotation? quote ('hello ==) (false) if) find

Leaving the issue open because quote-define is probably bugged.

[mwgkgk]

The above solution is polluting the stack! Which also causes the code in first quotation to execute if we go into the (false) branch. So it's not a good workaround.

[h3rald]

Hi again!

Yes, I’ll look into adding more permissive predicates to cover those use cases as well, it makes sense.

Concerning quote-define... There is a bug in the docs! # is the sigil for quote-bind while for quote-define you have to use =.

[mwgkgk]

More info:

  ("hello" puts!) "a" =

Fails with [=]: Undefined symbol '=', despite it being defined in the source:

  def.sigil("=") do (i: In):
    i.push("quote-define".newSym)

This works:

  ("hello" puts!) "a" quote-define

[h3rald]

OK so for now:

• I added the # and a = symbols (previously only sigils were defined) as shortands for quote-bind and quote-define respectively.
• I made == more permissive, it will now simply return false if types don't match.

[mwgkgk]

Beautiful!

One more question on comparisons: how to safely find a function in a quote?

("hello" puts!) :experiment
(1 2 3 experiment) (quote 'experiment ==) find

The predicate function above starts with quote because unquoted experiment is not equal to 'experiment. The problem is though that find is executing experiment (by placing it on stack?) before the predicate comes into play. Same issue with reduce.

[h3rald]

Actually it turns out that all the predicates leave the element on the stack! Now, from the docs they should remove it after checking, so I am going to consider it a bug and change their behavior.

Also, I am planning on adding two new logical operators to allow short-circuiting: dequote-and and dequote-or, so you’ll be able to write things like this:

  (1 8 “a” 3 “b” 4 5 6) (:x (x number?) (x 5 <) dequote-and) filter
  # returns (1 3 4)

...without having to wrap checks in an if or when.

[mwgkgk]

I'm not sure if that's going to help with my find usecase, because the evaluation of the experiment there happens before the predicate gets evaluated, so it has nothing to compare against.

string? quotation? etc are indeed leaving the element on stack and push the boolean after it, my bad for not realizing the behavior was uninteded - because signatures in the docs clearly don't match. I used to work around it with nip.

[h3rald]

Your original use case now works with ==:

  (1 2 ‘test ‘hello 4 5) (‘hello ==) find 
  # returns 3

No need for the quotation? check anymore in this case.

[mwgkgk]

Problem is the symbol in array is a function call:

(1 2 3 experiment)

Rather than a quoted symbol:

(1 2 3 'experiment)

What I'm doing is parsing the source of a function. So it has actual calls rather than quoted calls

[h3rald]

Ahh ok got it. I could introduce a new quote-map symbol to quote the elements of a quotation without evaluating them... so you could write the following:

  (2 3 + 4 *) quote-map  (‘+ ==) find

Any better idea?

[mwgkgk]

This is an elegant solution: no find's, reduce's and who-knows-what-else's need to be touched.