ShenDoc 30

The Primitive Functions of KLambda

The following set represents the set of 46 primitive functions which Shen requires and which are used in Kλ. All other functions are included in the Shen sources. The CL definitions are given to explain the semantics of these functions. Note in some cases these primitives can be reduced still further (e.g and in terms of if etc). In fact lambda alone is sufficient, but impractical. The instruction set is therefore a balance between economy of primitives (easy to implement but inefficient in execution) and practicality (more difficult to implement but possibly faster).

Kλ uses strict applicative order evaluation except for the boolean operations etc. which follow the usual pattern. NIL is just a symbol with no special status. () denotes the empty list.

Boolean Operations (4)

if	boolean test	boolean --> A --> A --> A
and	boolean and	boolean --> boolean --> boolean
or	boolean or	boolean --> boolean --> boolean
cond	case form	none

Symbols (1)

intern

maps a string containing a symbol to a symbol

none

Strings (7)

pos	given a natural number 0 ... n and a string S returns the nth unit string in S	string --> number --> string
tlstr	returns all but the first unit string of a string	string --> string
cn	concatenates two strings	string --> string --> string
str	maps any atom to a string	A --> string
string?	test for strings	A --> boolean
n->string	maps a code point in decimal to the corresponding unit string	number --> string
string->n	maps a unit string to the corresponding decimal	string --> number

Assignments (2)

set	assigns a value to a symbol	(value X) : A; X : symbol; Y : A; ______________ (set X Y) : A;
value	retrieves the value of a symbol

Error Handling (3)

simple-error	prints an exception	string --> A
trap-error	evaluates its first argument A; if it is not an exception returns the normal form of A else applies its second argument to the exception	A --> (exception --> A) --> A
error-to-string	maps an exception to a string	exception --> string

Lists (4)

cons	add an element to the front of a list	A --> (list A) --> (list A)
hd	take the head of a list	none
tl	return the tail of a list	(list A) --> (list A)
cons?	test for non-empty list	A --> boolean

Generic Functions (7)

defun	basic Lisp function definer	none
lambda	lambda function	X : A >> Y : B; _____________________ (lambda X Y) : (A --> B);
let	local assignment	Y : B; X : B >> Z : A; _______________ (let X Y Z ) : A;
=	equality	A --> A --> boolean
eval-kl	evaluation function	none
freeze	creates a continuation	A --> (lazy A)
type	labels the type of an expression	X : A; ___________ (type X A) : A;

Vectors (4)

absvector	creates a vector in the native platform	none
address->	destructively assigns a value to a vector address	none
<-address	retrieves a value from a vector address	none
absvector?	recognises vectors	A --> boolean

Streams and I/O (6)

write-byte	writes an unsigned 8 bit byte to a stream	number --> (stream out) --> number
read-byte	reads an unsigned 8 bit byte from a stream	(stream in) --> number
open	open a stream	if D = in or D = out Path : string; _______________ (open P D) : (stream D);
close	close a stream	(stream A) --> (list B)

Time (1)

get-time

get the run/real time

symbol --> number

Arithmetic (9)

+	addition	number --> number --> number
-	subtraction	number --> number --> number
*	multiplication	number --> number --> number
/	division	number --> number --> number
>	greater than	number --> number --> boolean
<	less than	number --> number --> boolean
>=	greater than or equal to	number --> number --> boolean
<=	less than or equal to	number --> number --> boolean
number?	number test	A --> boolean

Total 46 functions

Acknowledgements
Kλ
History
Basic Types in Shen and Kλ
The Primitive Functions of Kλ
The Syntax of Kλ
Notes on the Implementation of Kλ
Boolean Operators
The Syntax of Symbols
The Semantics of Symbols in Shen and Kλ
Packages
Prolog
Shen-YACC
Strings
Strings and Pattern Matching
Lists
Streams
Character Streams and Byte Streams
Bytes and Unicode
Reader Macros
Vectors
Standard Vectors and Pattern Matching
Non-standard Vectors and Tuples
Equality
I/O
Generic Functions
Eval
Type Declarations
External Global Variables
Property Lists and Hashing
Error Handling
Numbers
Floats and Integers
The Timer
Comments
Special Forms