Java-TPMV-Compiler

It is a very simple imperative language compiler into bytecode. This virtual machine is also capable of executing the generated code using its simulated CPU, Stack and Memory.

Source program grammar

• SourceProgram ::= Instruction1 . . . Instruction
• Instruction ::= SimpleAssignment | CompoundAssignment | While | If | Write | Return
• SimpleAssignment ::= Variable = Term
• CompoundAssignment ::= Variable = Term ArithmeticOper Term
• While ::= while BooleanCond SourceProgram endwhile
• If ::= if BooleanCond SourceProgram endif
• Write ::= write Variable
• Term ::= Variable | Number
• ArithmeticOper ::= + | - | / | *
• Variable ::= a | . . . | z
• Number ::= any integer number
• BooleanCond ::= Term BooleanOper Term
• BooleanOper ::= = | != | <= | <

Virtual Machine available commands

• HELP: it shows the description of the following commands.
• QUIT: closes the virtual machine.
• LOAD FICH: loads the file named FICH as the source program. It doesn't check the syntax.
• REPLACEBC N: asks for a new bytecode instruction and replaces the line N of the bytecode program by the new introduced instruction.
• COMPILE: does the lexical analysis of the source program, generating a new parsed program and, later from the parsed program generates a bytecode program.
• RUN: executes the bytecode program.

Examples

A while instruction looks like this:

while BooleanCond
instruccion_1
instruccion_2
...
endwhile

And a if one should look as below:

if BooleanCond
instruccion_1
instruccion_2
...
endif

Nested whiles source program example

x = 5
r = 0
while 0 < x
y = x
s = 1
while 0 < y
s = s * y
y = y - 1
endwhile
write s
r = r + s
x = x - 1
endwhile
return
end

Credits

• Built from scratch by David Arroyo