[Haskell-cafe] Re: Diagnosing stack overflow

Matthew Brecknell wrote:

The key point of the example is that foldl itself doesn't need any of the intermediate values of the accumulator, so these just build up into a deeply-nested unevaluated thunk. When print finally demands an integer, the run-time pushes a stack frame for each level of parentheses it enters as it tries to evaluate the thunk. Too many parentheses leads to a stack overflow. Of course, the solution to the example is to use

What is the point in building this huge thunk if it can't be evaluated without a stack overflow? Could the runtime do partial evaluation to keep the thunk size down or would that cause semantic breakage? Joe Buehler