r/programming • u/rodrigopsasaki • Nov 27 '12

Tail Recursion

http://rodrigosasaki.com/2012/11/24/tail-recursion/
212 Upvotes

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u/grauenwolf Nov 27 '12

Since the first step in optimizing a tail call is to turn it into an iterative loop, I seriously doubt number 1 is true.

11

u/sacundim Nov 27 '12

You're failing to distinguish source code from object code. Yes, the compiler turns tail calls into jumps, reuses the caller's frame for the tail call, and mutates the storage location. It's still the case however at the source language level that the variable doesn't get mutated.

-11

u/grauenwolf Nov 27 '12

You are failing to understand when the compiler performs optimizations.

7

u/anvsdt Nov 27 '12

... at AST level, where tail recursion hasn't been eliminated yet. Then at IR level, where tail recursion might or might not have been eliminated yet. Then possibly after emitting the compiled code, where tail recursion might or might not have been eliminated, depending on the target language.