Dear Vag,

Vag wrote:
To put in the nutshell, my point is that dag rewriting is better than graph rewriting as `base' of pure functional programming languages without manual proofs.
Better in the sense easier to reason about: I agree.
Better in the sense we do not need cycles: strongly disagree. There are algorithms that only have a reasonable complexity/efficiency due to a cycle. Without cycles we would need a more complex algorithm to mimic the effect. Cycles are nor used every day, but they do occur in real programs (not just Hamming numbers).

Consider a compiler that translates statements to machine instructions. This compilers yields the statements as well as the actual address for all labels used (in a tuple or record). These positions are feed to the compiler in order to generate the correct jumps. You can do this very elegantly with a cycle. If you cannot make this cycle you will probably need a two stage solution.

Best, Pieter
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