Guido Krüger's Web Service

LScript Short Reference

Lexical tokens

The scanner recognizes the following symbols:

Token Regular expression
whole number [0-9]+
floating point as defined in java.lang.Double
string ".*" (must not contain " itself)
lparen (
rparen )
quote ['~]
comment ;.*[$;]
whitespace [\t\r\n ]
delimiter [()\t\r\n ] (note: not ['";])

Token	Regular expression
whole number	[0-9]+
floating point	as defined in java.lang.Double
string	".*" (must not contain " itself)
lparen	(
rparen	)
quote	['~]
comment	;.*[$;]
whitespace	[\t\r\n ]
delimiter	[()\t\r\n ] (note: not ['";])

To simplify inclusion of LScript code into the arguments of an APPLET tag, the following additions to usual LISP syntax have been made:

The quote sign may be either ' or ~
Comments are started with ; and terminated at the end of the line or after the next ; (whatever occurs first).
Note that there are very few delimiters in the language. This allows for characters like '+' or '-' in function names but sometimes requries additional whitespace for delimiting.

Terms

There are four kinds of terms the expression evaluator understands:

Term Example Evaluation
number 12 or 3.14 Evaluates to itself
string "hello" Evaluates to itself
symbol add1 The value of the variable of this name
list (add1 5) A call to function with the name of the first element in the list. The other list elements are passed as arguments to the function.

Term	Example	Evaluation
number	12 or 3.14	Evaluates to itself
string	"hello"	Evaluates to itself
symbol	add1	The value of the variable of this name
list	(add1 5)	A call to function with the name of the first element in the list. The other list elements are passed as arguments to the function.

The interpreter simply works by fetching and evaluating the next term from the input until EOF is reached or an error occured. If a function argument is quoted, it is not evaluated before being passed to the function. Some functions don't require quoting for certain arguments which are used unchanged (i.e. setq). Any term is allowed for predicate functions. As usual, the empty list is considered false, all other values true. The return value of boolean function is either the empty list (false) or the symbol T (true). Literals are NIL and T, respectively.

Argument notation

Character	Meaning
N	Number
S	String
Y	Symbol
L	List
?	Any
*	Zero or more of the preceeding

The CorePlugin

func name	arguments	Purpose
eval	?	evaluates the argument
identity	?	returns the argument unchanged
progn	?*	block of statements
cond	(P ?)*	conditional statement
while	P	while loop
print	?*	Console output
println	?*	Console output with newline
quit		Terminates program
break		Terminates enclosing loop

The NumberPlugin

func name	arguments	Purpose
+	N*	Addition
-	N*	Subtraction
*	N*	Multiplication
/	N*	Division
%	N*	Remainder
add1	N	Add 1
sub1	N	Subtract 1
abs	N	Absolute value
sqrt	N	Square root
int	N	Whole number part
frac	N	Fractional part
pow	NN	Power
inv	N	Inverse value
round	N	Rounded to the nearest integer
sin	N	Sin
cos	N	Cos
tan	N	Tan
asin	N	ArcSin
acos	N	ArcCos
atan	N	ArcTan
random	N or NN	Random number
log	N	Logarithm to base e
exp	N	Exponential function to base e
max	N*	Maximum element
min	N*	Minimum element

variable	Purpose
PI	pi
E	e (base of natural log)

The StringPlugin

func name	arguments	Purpose
left	SN	left substring
right	SN	right substring
substr	SNN	mid substring
len	S	length
concat	S*	Concatentation
indexof	SS	Index of first occurrence of substring
tostring	?	String representation of term

The PredicatePlugin

func name	arguments	Purpose
<	NN or SS	less than
<=	NN or SS	less than or equal
>	NN or SS	greater than
>=	NN or SS	greater than or equal
=	NN or SS	equal to
!=	NN or SS	not equal to
not	?	true if term is empty list, false otherwise
and	?*	true if all arguments are true
or	?*	true if any argument is true

The GraphicPlugin

func name	arguments	Purpose
setcolor	NNN	foreground color (RGB value)
setbackground	NNN	background color (RGB value)
drawline	NNNN	draw line from x1,y1 to x2,y2
drawstring	SNN	draw string at x,y
drawrect	NNNN	draw rect at x,y of size w,h
fillrect	NNNN	filled rect
drawoval	NNNN	draw oval at x,y of size w,h
filloval	NNNN	filled oval
drawarc	NNNNNN	like oval, plus start and size angle
fillarc	NNNNNN	filled oval
setfont	SNN	set font family, style and size