Table of ContentsThe Scheme Programming Language Scheme philosophy Scheme Locally available versions C vs. Scheme expressions Prefix vs. infix Nested expressions 1 Nested expressions 2 Nested expressions 3 Nested expressions 4 Nested expressions 5 Evaluating arguments Types More types What’s in a symbol? Some “literals” evaluate to themselves Symbols evaluate by variable lookup define special form Lists evaluate by procedure application* Special forms List evaluation Creating a symbol’s value Suppressing evaluation quote special form Quoting Forcing evaluation with eval The Lambda Calculus Creating procedures with the lambda special form A moment for syntax Naming a procedure Shorthand for procedure definition Procedures vs. variables Conditionals: if special form C vs. Scheme C vs. Scheme eq? procedure tests for identity equality Recursion Linear recursive process Lists are made of cons cells cons cells and the cons procedure List syntax shorthand car, cdr, and friends Nested lists Do not try this at home our-list-ref procedure our-list-ref trace Linear iterative process Contrast the inductive steps Tail-recursion our-list-ref tail recursion Re-binding is NOT assignment Thinking recursively Recursion is about being a smart-aleck! Recursion templates Augmenting recursion examples More augumenting recursion Reducing functions Tail recursive version of factorial Tail recursive factorial trace Conditional augumentation Insertion sort Nested procedure defines Factoring out common sub-expressions let special form Scope is visibility let bindings happen in parallel Bad let bindings let* special form More about conditionals: cond special form cond example Short-circuiting and, or special forms Boolean values & and, or Procedures are first-class values map, a higher-order function Filter procedure Typechecking predicates Procedure factories Building procedures Dr. Scheme Graphics lambdas and closures lambdas and their environments Free variables and Lexical Scoping Dynamic Scoping Lexical vs. Dynamic Scope Lexical scope and variable hiding When the arguments don’t fit A more direct approach: the apply procedure Procedure arity Rest arguments Controlling evaluation inside of lists quasiquote and unquote Forcing and suppressing evaluation are fundamental Comparisons eq?, eqv?, equal? More eq?, eqv?, equal? Objects/values in the Scheme Heap Do not use eq? for numbers Making new lists Sharing of list structure append must duplicate the list List surgery set-cdr! and set-car! Assignment set! procedure Other side-effects Sequencing and the begin special form Side effects and Scwm for-each procedure Commenting example Commenting style Memory management Scheme memory model A view of garbage Mark and sweep garbage collection Reference counting Reference counting never reclaims cycles Mark and sweep vs. Reference counting |
Author: Greg J. Badros & Alan Borning |