ABM-Compiler-Python

What is ABM language? Abstract Machine Language.

The rule:

1. Stack Manipulation

• push c Pushes c onto the stack
• rvalue l Pushes contents of data location l onto the stack
• lvalue l Pushes address of data location l onto the stack
• pop Throws away value on top of the stack
• := Stack top is placed by the lvalue below it and both are popped
• copy Pushes a copy of the top value on stack

2. Control Flow

• label l Targets of jumps to l
• goto l Next instruction is taken from statement with label l
• gofalse l Pops the top value of the stack and jumps if it is zero
• gotrue l Pops the top value of the stack and jumps if if is nonzero
• halt Stops execution

3. Arithmetic Operators

• •       Adds top two values on stack and places result on stack
    

• − Similar to +, but subtraction is performed
• ∗ Similar to +, but multiplication is performed
• / Similar to +, but integer division is performed
• div Similar to +, but remainder of division is performed

4. Logical Operators

• & Logial AND the top two values on stack and places result on stack
• ! Negates the top of the stack
• | Similar to &, but logical OR is performed

5. Relational Operators

• <> Returns 0 if top two values on stack are equal otherwise returns 1
• <= Similar to <>, but tests if top minus one is less or equal top

• = Similar to <>, but tests if top minus one is greater or equal top

• < Similar to <=, but tests if top minus one is less than top

•       Similar to >=, but tests if top minus one is greater than top
  

• = Similar to <>, but tests if top minus one is equal to top of stack

6. Output

• print Writes top of the stack contents to output device
• show Writes a literal string to output device

7. Subprogram Control

• begin Marks the beginning of parameter passing and subroutine call
• end Marks the end of parameter passing and subroutine call
• return Returns from subroutine
• call Subroutine call