Tail-Recursive Function Transformation in Python

Thu, 22 Aug 2013 19:57:00 +0000

Intro

In 1986, Hal Abelson and Gerald Jay Sussman recorded some videos for their M.I.T. EECS course on the Structure and Interpretation of Computer Programs. Twenty-seven years later, these videos are still a great resource. But the language featured is the Scheme¹ dialect of Lisp and while I can/do follow along in “edwin”, sometimes it’s nice to play in a (language (with (less (parens)))), like python.

One of the early challenges that I faced while trying to follow a scheme course using python was Scheme’s heavily tail-recursive programming idiom. Here’s a toy example from the videos where we define a Peano addition operation that only uses increment and decrement.

Scheme on galvanist

Tail-Recursive Function Transformation in Python

Intro