[Haskell-beginners] recursive 'let' ?

[Kim-Ee Yeoh]

On Mon, Apr 14, 2014 at 11:24 AM, John M. Dlugosz
<ngnr63q02 at sneakemail.com>wrote:

> I don't mind recursive *functions*.  It's recursive definition of single
>> computed values that looked odd to me.  Lazy evaluation makes all the
>> difference.  Looking at
>>         b= f a c
>>
>>         c = f a b
>> I was thinking, "how can it figure out what b and c need to be?" because
>> I'm used to this meaning that it needs to come up with an actual value
>> right now.
>>
>>

To amplify Arjun's point,

    b = f a c
    c = f a b

is equivalent to

    b = f a (f a b)
    c = f a (f a c)

and now the mutual recursion that's troubling John vanishes.

They become plain ol' self-recursive functions.

I don't think mutual recursion is harder to make sense of than
self-recursion. I think self-recursion appears easier than mutual
recursion, but that's deceptive. It's actually just as hard!



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