clear semantics of function equality

[jmid]

Consider

let v = (=) bool_of_string bool_of_string in ""

With BuckleScript 1.8.0 (Using OCaml4.02.3+BS ) it compiles to:

// Generated by BUCKLESCRIPT VERSION 1.8.0, PLEASE EDIT WITH CARE
'use strict';

var Caml_obj   = require("bs-platform/lib/js/caml_obj.js");
var Pervasives = require("bs-platform/lib/js/pervasives.js");

Caml_obj.caml_equal(Pervasives.bool_of_string, Pervasives.bool_of_string);

/*  Not a pure module */

However the comparison of the (identical) funtional values succeeds at run time,
contrary to the specification of (=) http://caml.inria.fr/pub/docs/manual-ocaml/libref/Pervasives.html
and OCaml's bytecode backend, which errors with Exception: Invalid_argument "equal: functional value".

[OvermindDL1]

Well with javascript you cannot do function equality testing 'efficiently', however you can get the string representation of a function and compare those string's.

As for the spec, I think it would be nice to follow it in this case, function equality testing should be disallowed (I'd prefer at the type level generically, but for that we need Implicit Modules). This has caught up other people while using buckelscript-tea when they try to test function equality when they really really should not be doing so.

[bobzhang]

the thing is if we follow the spec, then we should always check if the operand is a function or not even if they are reference equal, which would cause unnecessarily slow down for no clear benefit

[jmid]

Since you are already generating a call to a specialized equality operator Caml_obj.caml_equal and since you have access to the static types in the compiler, I suppose it is an option to supplement with another (more expensive) specialized equality operator that has the right OCaml semantics for function equality and decide statically whether to generate a cheap or more expensive equality call?

[stale]

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