Re:SICP is Under Attack
by btilly on Thursday August 04, 2011 @09:00PM
(#2848519)
I think that the point was that the AST for a Scheme program isn't that different from the AST for a Python program, even though the code looks different.
Unfortunately that point is false as well. The AST for a Python program will generally involve a lot of message dispatches that won't exist in the AST for a similar Scheme program.
To get a sense of the difference, in Python if you yield, your code actually gets turned into a class with certain methods that get called repeatedly, and restart your method at the correct place with the correct state. By contrast equivalent code in Scheme will somewhere under the hood have call-with-current-continuation, which works by very different mechanics.
Unfortunately that point is false as well. The AST for a Python program will generally involve a lot of message dispatches that won't exist in the AST for a similar Scheme program.
To get a sense of the difference, in Python if you yield, your code actually gets turned into a class with certain methods that get called repeatedly, and restart your method at the correct place with the correct state. By contrast equivalent code in Scheme will somewhere under the hood have call-with-current-continuation, which works by very different mechanics.