IPP project 2022/23

parse.php

This script reads IPPcode23 code from the standard input, checks its lexical and syntactic correctness and prints its XML representation to the standard output according to the assinged specification.

Run

parse.php < [IPPCODE23] > [OUTPUT.xml]

Help

parse.php --help

interpret.py

This interpreter reads the XML representation of the IPPCode23 code from the file given by the --source parameter.

Run

interpret.py [-h] [--source SOURCE] [--input INPUT]
-h, --help show this help message and exit
--source SOURCE File with XML representation of source code
--input INPUT File with inputs for interpretation of source code\

Program flow

Interpret.py first of all parses the parameters given from the command line and creates a brief help for them (see the previous block titled Run). Then, using the xml.etree.ElementTree library, it sequentially loads individual XML elements, checks their semantic correctness, and creates new instances of the instructions and arguments classes

Object design

This implementation uses only three classes, which turned out to be a quite suboptimal solution. These classes are instruction, argument and variable. All of them use the protected Python convention.

Class instruction

• order - the order in which instructions are executed
• opcode - identifies what the instruction represents
• args[] - an array of up to three arguments for the instruction
• get_type(), get_value() - getters to get values from an object

class argument

• arg_type
• value
• set_type(), set_value()
• get_type(), get_value()

class variable

• name
• var_type
• value
• set_type(), set_value()
  • setter for name is not needed, because the variable name is added only when the variable is initialized and never changes
• get_name(), get_type(), get_value()

Functions

Since this implementation doesn't take the full advantage of the object oriented approach, it uses a large number of functions. The most important are:

• interpreter - a finite state machine for interpreting commands, calls the function interpreter_XY, where XY is the name of the command. This is a nice example of code which would be better OO.
• add_arg2ins - adds all arguments to the instruction, probably should have been a class method of instruction