Introduction

When was the original Lisp designed?
The original Lisp was designed in 1958.

Who designed the original Lisp?
The original Lisp was designed by John McCarthy.

What are the two main dialects of the original Lisp?
The two main dialects of the original Lisp are:

  1. Scheme.
  2. Common Lisp.

What is the only other programming language which is older than the original Lisp and by how long?
The only other programming language which is older than the original Lisp is Fortran by one year.

Has Fortran changed drastically?
Yes, Fortran has changed drastically.

Has Lisp changed drastically?
No, Lisp hasn't changed drastically.

What paradigm is the pure subset of Lisp?
The pure subset of Lisp is functional.

What is the pure subset of Lisp based on?
The pure subset of Lisp is based on the lambda calculus of Alonzo Church.

Quote by Jorge Santayana

Those who cannot remember the past are condemned to repeat it.

Those who don't know Lisp are doomed to ... ..., ...
Those who don't know Lisp are doomed to reinvent it, poorly.

What are the features of Scheme?
The features of Scheme include:

  • Extremely simple syntax for programs and data.
  • Strongly and dynamically typed.
  • Statically scoped.
  • Higher-order - Functions are first-class objects which can be constructed and evaluated during execution.
  • Embeddable - Guile (Scheme dialect) is used in programs such as GnuCash, LilyPond, GNU Guix, GNU Debugger, GNU TeXmacs, GNU Make, and Google's Schism.
Example of a GNU makefile which uses Scheme code through the Guile interpreter
# PATH=/bin:/usr/bin LD_LIBRARY_PATH= make

all:
	echo $(addsuffix .class,$(basename $(wildcard *.java)))
	$(guile (let ((msg (list "Hello " "world\n"))) \
		(display (car msg)) \
		(display (cadr msg))))

Program structure

What is a Scheme program made up of?
A Scheme program is made up of a set of function definitions followed by a sequence of function calls.

What is the function definition syntax in Java?
The function definition syntax in Java is:

What is the function definition syntax in Scheme?
The function definition syntax in Scheme is:

What is the function call syntax in Java?
The function call syntax in Java is:

What is the function call syntax in Scheme?
The function call syntax in Scheme is:

What does an open parenthesis always mean in Scheme?
In Scheme, an open parenthesis always means you're calling a function.

Example of a Scheme program which defines a recursive function for summing a sequence of numbers, calls it, and displays the results
;; Scheme sum program

(define (sum seq)
	(if (null? seq)
		0
		(+ (car seq) (sum (cdr seq)))))

(display (sum '(5 6 1 8 3 7)))
(display "\n")

What does the abbreviation 'x mean?
The abbreviation 'x means (quote x).

What does the abbreviation '(...) mean?
The abbreviation '(...) means (quote (...)).

What does the built-in function quote return?
The built-in function quote returns its one parameter, unevaluated.

What is a function definition in Scheme?
In Scheme, a function definition is a call to a function called define which defines a function.

Example of a Scheme program which defines a tail recursive function for summing a sequence of numbers, calls it, and displays the results
;; Scheme sum program

(define (sum seq)
	(define (sum seq res)
		(if (null? seq)
			res
			(sum (cdr seq) (+ res (car seq)))))
	(sum seq 0))

(display (sum '(5 6 1 8 3 7)))
(display "\n")

What does the built-in function car do?
The built-in function car returns the first value in a sequence.

What does the built-in function cdr do?
The built-in function cdr returns all of the values in a sequence except the first.

What can a translator or compiler do if it recognizes a tail recursive function?
If a translator or compiler recognizes a tail recursive function, it can optimize the translated or compiled code by utilizing jump instructions.

Does the define function cause a side effect?
Yes, the define function causes a side effect.

Can the define function redefine a symbol?
Yes, the define function can redefine a symbol.

Is the define function an imperative feature and when?
Yes, the define function is an imperative feature if misused.

What makes a function definition and a variable definition similar in Scheme?
In Scheme, a function definition and a variable definition are similar in that both simply bind a value to a symbol (its name).

What makes a function definition and a variable definition dissimilar in Scheme?
In Scheme, a function definition and a variable definition are dissimilar in that the type of the value is different.

How do you denote a callable value in Scheme?
In Scheme, you denote a callable value with (lambda ...).

Example of defining a named function in Scheme with the define function, calling it, and displaying it
guile> (define (f x) (+ 1 x))
guile> (f 123)
$1 = 124
guile> f
$2 = #<procedure f (x)>
Example of defining a variable in Scheme to hold the returned value of the + function
guile> (define f (+ 1 123))
guile> f
$1 = 124
Example of defining a variable in Scheme to hold a function created with the lambda function
guile> (define f (lambda (x) (+ 1 x)))
guile> (f 123)
$1 = 124
guile> f
$2 = #<procedure f (x)>
Example of calling a function created by the lambda function without giving it a name
guile> ((lambda (x) (+ 1 x)) 123)
$1 = 124

Syntax and Semantics

...

What does a Scheme program consist of?
A Scheme program consists of symbolic expressions called S-expressions.

What does a literal evaluate itself to?
A literal evaluates itself to itself.

What does a symbol evaluate to/
A symbol evaluates to its defined value.

What does a paranthesized sequence of S-expressions evaluate to?
A paranthesized sequence of S-expressions evaluates to the return value of first S-expression in the sequence being called as a function and the remaining S-expressions being passed to that function as parameters.

How are some parameters to some functions evaluated?
Some parameters to some functions are evaluated after the function call.

Translation

...

List representation

...