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aforadi
08-03-2008, 04:01 PM
Data Structures Assignment 1
Due: Aug 10, 5pm
(Submit at moodle.)

Write an interpreter for the following language. Define and use a Procedure class that stores information about one procedure, i.e., the list of its instructions. The instructions are stored parsed: i.e., as < OPERATION-CODE, OPERANDS > tuple. You may choose any representation for op codes (but make sure that you use no literal constant in any of your methods). You need classes Program Instruction, OpCode and Operand. Classed Program and Procedure should each have the execute method that sequentially executes its Instructions. You will also need a VirtualMachine class (that will have your main program) as well as a Parser class. Make sure you handle exceptions (wrong input programs). The execute method for the PRINT instruction may directly call the JAVA print function.
Syntax
COMMENT string
DEFINEPROC procedurename parametername
SET variablename anothervariablename/value
ENDPROC
CALLIF variablename/value procedurename variablename/value
PRINT variablename

Details
All procedures take one input parameter and return no values
The input parameter can only be an integer (of arbitrary size)
All calls are by value
Recursion is allowed
No global variables
Only integer constants -- but of arbitrary width
Each program must have an entry procedure named "start".
CALLIF calls the function if the first operand is non-zero; the last operand provides the parameter value.
Example Code

COMMENT This is a comment
DEFINEPROC recur level
PRINT level
CALLIF level recur level-1
ENDPROC

DEFINEPROC start
SET call 1
CALLIF call recur 3
ENDPROC


Expected Output

3
2
1
0

COULD ANYONE EXPLAIN ME THE PROBLEM FIRST? I HAVE NO CLUE AT ALL.

ralph l mayo
08-04-2008, 07:02 AM
Congratulations on coming up with the worst thread title I've ever seen here, and with some very stiff competition too.

If you don't understand this question you should probably just drop the class. You are expected to produce a Java program that compiles this limited grammar to some arbitrary instruction set, and write a (presumably also Java) virtual machine that interprets and executes the instruction set.

borntoslow
08-07-2008, 08:55 AM
hahaha ralph, best reply to a post i have ever seen.



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