About this project

The purpose of this project is to make a compiler in Java that checks whether or not a minipython file has any lexical/syntax errors.

• Minipython implements the following:
  • Assigning integers, decimals and strings.
  • Assigning lists to variables.
  • Declaring functions with simple arguments or with default values.
  • If, print, while, for functions.
  • Function calls.
  • Single line comments.

Contents

• About this project
• Contents
  • Example of minipython code
  • BNF for MiniPython
• Implementation
  • Abstract Syntax Tree
    • How to run
  • Semantic Analysis
    • How to run

Example of minipython code

#A miniPython example

def fib(n):    # write Fibonacci series up to n
               a = 0
               b = 1
               while a < n:
                        print a
                        a = b
                        b = a + b
                      
def funcwithdef(name,university="aueb"):
       print name, " studies in ", university 

BNF for MiniPython

Implementation

Abstract Syntax Tree

• Creates the syntax tree of the given minipython file. You can either use example.py, exmple1.py or create your own python files and use those.

How to run

• Open cmd and navigate to where your files are located. From there do the following:
  • sablecc minipython.grammar
  • javac ASTTest.java
  • java ASTTest example.py
• The AST is printed in your terminal.

Semantic Analysis

Implements two visitors that check for the following in a given minipython file:

1. Use of undeclared variable. A variable is considered declared if it is assigned a value or if it is used as an argument in a function declaration, all variables are global.

def add(x,y):
   return x + y
print k

The following code is wrong because the variable is used before declaration.

def add(x,y):
   return x + y
print k
k = 0

2. Calling an undeclared function (here a function can be used before the declaration).

3. Incorrect argument definition in function call.

The following code is correct.

def add(x,y=2):
   return x + y
print add(1)

4. Using a variable of a different type (eg Integer with String) as an integer.

def add(x,y):
   return x + y
k="hello world"
print add(2,k)

5. Arithmetic expressions in which the following are used as operators: None, type(variable)

6. Incorrect way of using a function call

def add(x,y):
   return "hello world"
print add(2,1)+2

7. Function overload

The following is wrong (Both functions need at least 2 arguments)

def add(x,y):
def add(x,y,z=1)

The following is wrong (Both functions need at most 3 arguments)

def add(x,y,z):
def add(x,y,z=1)

How to run

• Open cmd and navigate to where your files are located. From there do the following:
  • sablecc minipython.grammar
  • javac ParserTest.java
  • java ParserTest example.py
• If there are semantic errors, they will be printed in your terminal.