#reader(lib"read.ss""wxme")WXME0108 ## #| This file uses the GRacket editor format. Open this file in DrRacket version 5.3.6 or later to read it. 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The" #"y record metadata" ) 0 0 4 29 1 #"\n" 0 0 4 3 85 ( #";; about the language level of this file in a form that our tools ca" #"n easily process." ) 0 0 4 29 1 #"\n" 0 0 4 3 194 ( #"#reader(lib \"htdp-intermediate-lambda-reader.ss\" \"lang\")((modnam" #"e |#lect20b-scope|) (read-case-sensitive #t) (teachpacks ()) (htdp-s" #"ettings #(#t constructor repeating-decimal #f #t none #f ())))" ) 0 0 4 29 1 #"\n" 0 0 23 3 1 #"(" 0 0 14 3 7 #"require" 0 0 23 3 1 #" " 0 0 19 3 20 #"\"student-extras.rkt\"" 0 0 23 3 1 #")" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 17 3 65 #";;; READING: Sebesta 5.1-5.3; skim 5.4; 5.5 ('til 5.5.5 suffices)" 0 0 23 29 1 #"\n" 0 0 17 3 31 #";;; [that's about 13pp total]" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 23 3 1 #"(" 0 0 15 3 6 #"define" 0 0 23 3 1 #" " 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 20 3 1 #"7" 0 0 23 3 1 #")" 0 0 23 29 1 #"\n" 0 0 23 3 1 #"(" 0 0 15 3 3 #"let" 0 0 23 3 3 #" {[" 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 20 3 1 #"4" 0 0 23 3 1 #"]" 0 0 23 29 1 #"\n" 0 0 23 3 7 #" [" 0 0 14 3 1 #"z" 0 0 23 3 2 #" (" 0 0 14 3 1 #"+" 0 0 23 3 1 #" " 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 20 3 1 #"2" 0 0 23 3 3 #")]}" 0 0 23 29 1 #"\n" 0 0 23 3 3 #" (" 0 0 14 3 1 #"+" 0 0 23 3 1 #" " 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 14 3 1 #"z" 0 0 23 3 2 #"))" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 17 3 51 #"; 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but z is not." 0 0 23 29 1 #"\n" 0 0 17 3 57 #";; Note that x is *not* free inside the larger expression" 0 0 23 29 1 #"\n" 0 0 23 3 1 #"(" 0 0 15 3 3 #"let" 0 0 23 3 3 #" {[" 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 20 3 1 #"9" 0 0 23 3 2 #"]}" 0 0 23 29 1 #"\n" 0 0 23 3 3 #" (" 0 0 15 3 3 #"let" 0 0 23 3 3 #" {[" 0 0 14 3 1 #"z" 0 0 23 3 1 #" " 0 0 20 3 1 #"5" 0 0 23 3 3 #"]} " 0 0 23 29 1 #"\n" 0 0 23 3 5 #" (" 0 0 14 3 1 #"+" 0 0 23 3 1 #" " 0 0 14 3 1 #"x" 0 0 23 3 1 #" " 0 0 14 3 1 #"z" 0 0 23 3 3 #")))" 0 0 23 29 1 #"\n" 0 0 17 3 66 #";; (For a variable to be free within an entire program is probably" 0 0 23 29 1 #"\n" 0 0 17 3 36 #";; an error 'undeclared variable'.)" 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 17 3 79 ( #";;; \"alpha substitution\" -- lift to the top level, and re-name to " #"not conflict." ) 0 0 23 29 1 #"\n" 0 0 17 3 57 #";;; But only lift *free* occurrences in the expression." 0 0 23 29 1 #"\n" 0 0 23 29 1 #"\n" 0 0 17 3 68 ( #";;; \"beta reduction\" -- re-write the body of a function, with para" #"ms" ) 0 0 23 29 1 #"\n" 0 0 17 3 73 ( #";;; 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