liftM2 documentation seems not coherent with its implementation

[ilario-pierbattista]

Hi,

I was looking to the documentation of liftM2:

php-functional/src/Functional/functions.php

Line 384 in e5f9d60

* liftM2 :: Monad m => (a -> b -> c) -> m a -> m b -> m c

which is similar to the haskell version.

However the implementation seems to be wrong: $transformation is not used as a pure function.

php-functional/src/Functional/functions.php

Lines 396 to 415 in e5f9d60

	function liftM2(
	callable $transformation = null,
	Monad $ma = null,
	Monad $mb = null
	) {
	return curryN(
	3,
	function (
	callable $transformation,
	Monad $ma,
	Monad $mb
	) {
	return $ma->bind(function ($a) use ($mb, $transformation) {
	return $mb->bind(function ($b) use ($a, $transformation) {
	return $transformation($a, $b);
	});
	});
	}
	)(...func_get_args());
	}

It seems to be like bind2.
Am I missing something?

Thanks

[widmogrod]

@ilario-pierbattista grate finding! You're correct.

To make implementation valid. This change is required:

-return $transformation($a, $b); 
+return $ma::of($transformation($a, $b));

[ilario-pierbattista]

Why not just changing the latest bind to a map?

[widmogrod]

There are many roads to Rome. No particular reason.