"Marcin 'Qrczak' Kowalczyk" produced ....

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I brought up the same issue some time back about >>. That is in func = f x >> func, we have the problem that >> is a function so func is not a last call.

It's an easy problem: although func is not a tail call, >> is a tail call and >> itself in most monads enters its second argument in a tail position. I would name it an indirect tail call.

I'll take it for the moment that Marcin is not deliberately being obtuse and just emphasise what the word "problem" means. If I say to a primary school student that in arithmetic the problem is to work out such things as "what is 2+2" the student might respond with "that's not a problem, 2+2=4, even I know that". But, they missed the point they we were not saying that 2+2 was a difficult problem whose resolution was the aim of arithmetic, we are simply pointing out the nature of the problems that arithmetic is aimed at solving. To paraphrase my earlier comment, I start by taking it that the definition of "last call" is essentially when a function returns the return value from another function call. In this situation we can validly destroy the context of the caller, thus, for example, evaluating a tail recursive routine with constant resource usage, ceteris paribus. In something like fact n t = if n==0 then 1 else fact (n-1) (t*n) this is clearly the case. But in a traditional procedural code, we might say fact(n,t){if(!n) return 0; t=t*n; n=n-1; return fact(n,t);}. This is taken within the meaning of tail recursion, but a direct transliteration into Haskell means that the ; becomes >>=, which means that strictly the factorial is not a "last call". Nevertheless, the concept of last call optimisation still stands, due to the nature of the >>= operator. It stands here in a way that does not apply to fact(n){if(!n) return 1; return n * fact(n-1);}. (Of course other automated optimisations apply here, Marcin).

in a tail position. I would name it an indirect tail call.

To quote Spock ... I believe I just said that, Doctor. Regards, Bruce. ps: If Marcin wants to play anymore semantic games I promise he can do so on his lonesome.