Schemes and Lisps have memory model, it's just one that's radically different enough from processor memory models that no-one realizes it's a memory model and t

Schemes and Lisps have memory model, it's just one that's radically different enough from processor memory models that no-one realizes it's a memory model and thus no-one gripes about it being different from processor X's memory model. If you're wondering what the memory model is, you should ask yourself: What happens when I mutate a cell? are those changes visible in references to that cell? are those changes visible across thread boundaries? What happens when I dereference a cell? Does it continue to take up memory or is it garbage-collected? What if it's part of a cycle? But I digress; your point was actually about languages that don't talk about memory, such as the lambda calculus. A degenerate memory model is still a memory model, and an inherently portable one at that. My point is, for languages which do talk about memory, it's necessary that they specify how that memory works in order to be a portable language.