COMPSCI 61A Lecture Notes - Lecture 28: Eval, Universal Turing Machine, Tail Call

• School: Berkeley
• Department: Computer Science
• Course: COMPSCI 61A
• Professor: De Nero John

Document Summary

Way in which names are looked up in scheme and python is called lexical scope (or static scope) Lexical scope: parent frame is the environment in which a procedure was defined. Dynamic scope: parent of a frame is the enviornment in which a procedure was called. Define (f (lambda (x) (+ x y))) define g (lambda (x y ), (f (+ x x ))))) Lexical scope: parent for f"s frame is the global frame. Dynamic scope: parent for f"s frame is g"s frame. No re-asignment and no mutable data types name -value bindings are permanent. Val of expr is independ of order in wich sub-expressions are evaluated. Subexpressions can safely be evaluated in parallel or on demand. Referential transparency: val of expression does not change when we substitute one of its subexpressions with the value of the subexpression. Allows for memoization w/ worry of changing behavior over stuff. Functional programming lang can be just as efficient as regular.