Lisaac

Features

Communication protection mechanisms

Hardware facilities

System interrupt support

Driver memory mapping

Despite being compiled, all objects retain their dynamic abilities

Basic syntax

Lisaac is case sensitive. Keywords are capitalized (Section, Header, Public, …), type identifiers are written in upper case letters (INTEGER, BOOLEAN, OBJECT, …), and identifiers denoting variables and slots are written in lower case letters. Objects are composed of slots, which can be data or code. The ':' symbol is used to declare types. Slot names are prefixed with a '+' or '-' symbol to indicate whether the slot is local to an object or shared between objects.

Parentheses are used to delimit lists of semicolon separated statements. Statement lists may have zero, one or more return values. The ':=' symbol is used to bind a slot to a statement or statement list that is executed at the loading/initialization of an object. The '<-' symbol is used to bind a slot to a statement list that is executed on the call of the slot.

Dynamic inheritance

The parent of each object is just a slot that can be assigned as required in the code, for instance:

Section Header - name := DECOD_MPEG2_TO_SCREEN; Section Inherit - videoparent : OBJECT <- ( + result : OBJECT; typ .when 1 then { result := WINDOW;} .when 2 then { result := VIDEO_VGA;} .when 3 then { result := VIDEO_TVOUT;}; result ) Section Public - typ : INTEGER; - decode_stream <- ( putimage decode_to_bitmap; )

Operator redefining

In Lisaac, an operator is a slot and can be redefined. For example, overloading the + operator for a NUMERIC object:

- '+' Left 80 other:SELF :SELF <- Self - -other;

Or for a matrix:

- '+' Left 80 other:SELF :SELF <- ( + result : SELF; result := SELF.create count; 1.to tab.count do { i : INTEGER; result.put (item i+other.item i) to i; }; result )

Genericity

Generic objects are supported, for instance:

ARRAY(E), DICTIONARY(KEY,VALUE)

Contract programming

Contract programming using Z notation is provided.