Ackermann - Prequel Example

Enter two non-negative integer numbers.
(Note that the Ackermann function grows very rapidly, even for small inputs.)

Prequel program

Module: ACKERMANN

 IF ackermann IS UNDEFINED 
  ackermann = [ACKERMANN.INPUT] 
 ENDIF 
 m_n = ackermann.POP 
 IF m_n[0] == 0 
  IF ackermann.LENGTH == 0 
   ACKERMANN.RETURN(m_n[1]+1) 
  ENDIF 
  prev_m_n = ackermann.POP 
  prev_m_n.PUSH m_n[1]+1 
  ackermann.PUSH prev_m_n 
 ELIF m_n[1] == 0 
  m_n[0] -= 1 
  m_n[1] = 1 
  ackermann.PUSH m_n 
 ELSE 
  ackermann.PUSH [m_n[0]-1] 
  m_n[1] -= 1 
  ackermann.PUSH m_n 
 ENDIF

Input:

 ACKERMANN.INPUT 
  The list of values written in the editable text input. 
  -> e.g. [3, 2] 
  
 CALL.ARGS 
  Holds the list of arguments passed with CALL. 
  -> [arg1, ..., argN]

Procedures:

 ACKERMANN.RETURN(result) 
  End computation and show the calculated value. 
  -> result: calculated integer value 
  
 CALL(&retvar1, ..., &retvarM, @modname, arg1, ..., argN) 
  Start executing module modname, copying N arguments and expecting M return values. 
  -> retvar: name of variable to hold the corresponding return value retval 
  -> modname: name of module to start executing 
  -> arg: value to be copied to the list CALL.ARGS 
  Alternative syntax: retvar1, ..., retvarM = CALL(@modname, arg1, ..., argN) 
  Note that recursive module calls are not allowed. 
  
 RETURN(retval1, ..., retvalM) 
  Return M values from the current module. 
  Resume execution at the next instruction of the corresponding CALL. 
  -> retval: value to be copied to the corresponding variable retvar