Michael Fogus wrote:
I know some things about ClojureScript and would be happy to answer
any direct questions. However, I think its notion (and Clojure proper)
is that "functions are data are functions" is very powerful.
It's a great idea (I first met John McCarthy in 1977 when I was 16). Too
bad JS was not allowed to be "Scheme in the browser".
A lot of
interesting patterns fall out of this as others have pointed out.
I'm ready to jump in with both feet, except for JS's age and the
possibility that too much code on the web counts on things like
(typeof x == "function") <=> x() works and x.apply is the expected built-in
No problem, you say, we can leave typeof alone and add a callable
predicate and evangelize that. Ok, provided the callable protocol uses
an ES6 private name (think gensym), any public name could be in use and
make a false positive when testing callability.
So let's use a well-known private (unique, should say) name, e.g.
module std {
...
export const invokeName = Name.create("invoke");
export function callable(v) {
if (typeof v == "function")
return true;
if (typeof v == "object" && v != null)
return invokeName in v; // could be pickier but let's start here
return false;
}
}
// make an object obj be callable:
obj[invokeName] = function (...args) { /* ... */ };
Looks ok, ignoring details such as how the client code gets the standard
unique name binding (import invokeName from "@std" or some such).
One can't assume apply or call or other Function.prototype heritage is
in x just because callable(x) returns true. Callability is wider and
weaker than typeof-result "function".
IIRC, security conscious folks do not want an attacker to be able to
make any old object callable. Cc'ing Mark for his thoughts.
/be
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