| > Yes, this is the standard solution, and it's a good one because it has a robust cost model (no quadratic | costs). However, it's tricky to get right; copying is simpler. If a significant fraction of runtime (for some | interesting program(s)) turned out to be consumed by copying stacks then we could consider this. | | Do you really need such evidence? If we agree that allowing stack to | grow to arbitrary (limited only by memory availability) size is | reasonable then surely we already know that there will be some stack | size for which quadratic copying cost is going to get "stupid" :-) Indeed, in principle. But there are only so many GHC-HQ cycles. Fixing stacks means not fixing something else, so it matters which issues bite most users. This isn't a fixed-sum game. The more people help fix and improve GHC, the more we can focus on the tricky bits that only we can do. Simon