The SchemeProgramming 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 byvariable lookup

define special form

Lists evaluate byprocedure 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 withthe lambda special form

A moment for syntax

Naming a procedure

Shorthand forprocedure definition

Procedures vs. variables

Conditionals:if special form

C vs. Scheme

C vs. Scheme

eq? proceduretests for identity equality

Recursion

Linear recursive process

Lists are made of cons cells

cons cells and thecons procedure

List syntax shorthand

car, cdr, and friends

Nested lists

Do not try this at home

our-list-ref procedure

our-list-ref traceLinear iterative process

Contrast theinductive steps

Tail-recursion

our-list-ref tail recursion

Re-binding is NOT assignment

Thinking recursively

Recursion is aboutbeing a smart-aleck!

Recursion templates

Augmenting recursion examples

More augumenting recursion

Reducing functions

Tail recursive version offactorial

Tail recursive factorial trace

Conditional augumentation

Insertion sort

Nested procedure defines

Factoring outcommon sub-expressions

let special form

Scope is visibility

let bindings happenin parallel

Bad let bindings

let* special form

More about conditionals:cond special form

cond example

Short-circuiting and, orspecial 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 andtheir environments

Free variables andLexical Scoping

Dynamic Scoping

Lexical vs. Dynamic Scope

Lexical scopeand variable hiding

When the arguments don’t fit

A more direct approach:the apply procedure

Procedure arity

Rest arguments

Controlling evaluationinside of lists

quasiquote and unquote

Forcing and suppressingevaluation are fundamental

Comparisons

eq?, eqv?, equal?

More eq?, eqv?, equal?

Objects/values in theScheme Heap

Do not use eq? for numbers

Making new lists

Sharing of list structure

append mustduplicate the list

List surgery

set-cdr! and set-car!

Assignment

set! procedure

Other side-effects

Sequencing andthe 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 sweepgarbage collection

Reference counting

Reference countingnever reclaims cycles

Mark and sweep vs.Reference counting