SCI Programming Language/Introduction
The SCI language is an object-oriented language with a Lisp-like syntax. It is compiled by the sc compiler into p-machine code which is used by the interpreter, sci.exe. We will begin our discussion of the language with its basic Lisp-like characteristics, then go on to the object-oriented parts of the language. Like Lisp, SCI is based on parenthesized expressions which return values. An expression is of the form:
(procedure [parameter parameter...])
The parameters to a procedure may themselves be expressions to be evaluated, and may be nested until you lose track of the parentheses. Unlike Lisp, a procedure itself may not be the result of an evaluation. An example of an expression is:
(+ (-y 2) (/ x 3))
which would be written in infix notation as:
(y -2) + (x / 3)
All expressions are guaranteed to be evaluated from left to right. Thus,
(= x 4) (= y (/ (+= x 4) ( / = x 2)))
will result in y = 2 and x = 4.
Comments in SCI begin with a semicolon and continue to the end of the line.
Primitive Procedures
Arithmetic primitives
In the following examples, e1, e2, etc. are arbitrary expressions. Brackets [...] indicate optional entries. Procedures evaluate their parameters from left to right.
Addition
(+ e1 e2 [e3...])
evaluates to: e1 + e2 [+ e3...]
example: (+ 7 12 4) evaluates to 23.
Multiplication
(* e1 e2 [e3...])
evaluates to: e1 (*e2[*e3...]
example: (* 2 10 3) evaluates to 60.
Subtraction
(- e1 e2)
evaluates to : e1 - e2
example: (- 20 11) evaluates to 9.
Division
(/ e1 e2)
evaluates to: e1 / e2
example: (/ 24 6) evaluates to 4. <---- Note: does this round when necessary (up, down)?
Remainder
(mod e1 e2)
evaluates to: the remainder of e1 when divided by e2.
example: (mod 17 5) evaluates to 2.
Operation Shift Left
(<< e1 e2)
evaluates to : e1<< e2 where the << operation shifts its left hand side left by the number of bits specified by its right hand side.
example: (<< 7 2 ) evaluates to 28.
In binary: 111 << 2 = 11100
Operation Shift Right
(>> e1 e2)
evaluates to: e1 >> e2 (as in << except with a right shift)
example: (>> 7 2) evaluates to 1.
In binary: 111 >> 2 = 001
Bitwise Exclusive OR Operator
(^ e1 e2 [e3...])
evaluates to: e1^ e2 [^ e3...]
example: (^ 11 26) evaluates to 17.
In binary: 01011" 11010 = 10001
Bitwise AND Operator
(& e1 e2 [e3...])evaluates to: e1 &e2 [& e3...]
example: (& 11 26)evaluates to 10.In binary: 01011 & 11010 = 01010
Bitwise OR Operator
(| e1 e2 [e3...])evaluates to: e1 | e2 [| e3...]
example: (| 11 26) evaluates to 27.
In binary: 01011 111010 = 11011
Bitwise NOT
(~ e1)evaluates to: the bitwise not of e1 (all 1 bits are changed to 0 and all 0 bits are changed to 1).
example: (~ 11) evaluates to -12.
In binary: ~01011 = 1111111111110100 (all the leading 0s in the 16 bit number change to 1s).
- Notes
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