Re: Isn't this tail recursive?

Hal Daume III:

Here's the basic idea. Suppose we have the function:

...

sum [] acc = acc sum (x:xs) acc = sum xs (acc+x)

This is tail recursive, but not strict in the accumulator argument. ...

Just a nitpick here. sum is indeed strict in its second argument (given that (+) is strict in its first argument). That is, sum l _|_ = _|_ for all possible lists l. It is of course possible that the compiler you use does not detect this and generates nonstrict code. But I think a decent strictness analyzer should detect this. Can the problem be that + is overloaded in Haskell, so the compiler cannot assume any semantical properties like strictness for it? Björn Lisper