Basic stack-based interpreter for APT Lecture.
Runs with one stack, and a program counter (pc), that starts at 0.
Compile all three classes, then run Interpreter with one argument, your input file.
For example:
java Interpreter myfile.swl
| Name | Description |
|---|---|
PRINT |
Prints the top element |
INT x |
Pushes integer x to stack |
ADD |
Adds the top two elements |
SUB |
Subtracts the top two elements |
SWAP |
Swaps the two top elements |
DUP |
Duplicates top element |
POP |
Pops top element from stack (effectively just removes it) |
JGE x |
If top element is >=0, jump to x |
JEQ x |
If top element is ==0, jump to x |
CALL x |
Push pc+1 to stack, jump to x |
RET |
Pop top element, jump to it |
Lines can also be preceded by labels, the format for this is LABEL: INSTRUCTION
(note the space between the colon and the instruction)
INT 100
L1: PRINT
INT 1
SUB
JGE L1