How to make a compiler on Python

"Create your own Python compiler with this step-by-step guide and example code."

Creating a Compiler in Python

Creating a compiler in Python can be a lengthy process, but the rewards are great. A compiler is a computer program that takes a set of instructions written in a programming language and converts them into a language that the computer can understand. Writing a compiler in Python is a great way to learn about how programming languages work and gain experience with a powerful and versatile language.

The first step in creating a compiler in Python is to define the language you want to compile. This includes deciding on keywords, data types, and any other features you want your language to have. You'll need to create a grammar that describes the syntax of the language, as well as a lexer to tokenize the code. The lexer will take the code and break it down into individual tokens that can be used by the parser.

The parser is the component of the compiler that takes the tokens produced by the lexer and turns them into an abstract syntax tree (AST). The AST is a tree-like structure that represents the structure of the code, which can be used to generate code in the target language. This is usually done with a code generator, which takes the AST and produces code in the target language.

Finally, you'll need to implement a code optimizer to improve the efficiency of the code. This involves analyzing the code and making changes to improve its performance. It can involve adding type annotations, optimizing loops, or removing redundant operations. Once the code is optimized, it can be output to the desired target language.

To demonstrate how to create a compiler in Python, we can use the following example. This example will demonstrate how to create a compiler that translates a simple arithmetic expression into assembly language.

def lexer(source):
    tokens = []
    source = source.replace('(', ' ( ').replace(')', ' ) ').split()
    for token in source:
        if token.isdigit():
            tokens.append(('NUMBER', int(token)))
        elif token in ('+', '-', '*', '/'):
            tokens.append(('OPERATOR', token))
        elif token == '(':
            tokens.append(('LPAREN', token))
        elif token == ')':
            tokens.append(('RPAREN', token))
    return tokens

def parser(tokens):
    ast = []
    current = ['ROOT']
    for token_type, token_value in tokens:
        if token_type == 'NUMBER':
            current.append(('NUMBER', token_value))
        elif token_type == 'OPERATOR':
            current.append(('OPERATOR', token_value))
        elif token_type == 'LPAREN':
            ast.append(current)
            current = []
        elif token_type == 'RPAREN':
            parent = ast.pop()
            parent.append(tuple(current))
            current = parent
    ast.append(current)
    return ast[0]

def codegen(ast):
    instructions = []
    if ast[0] == 'ROOT':
        instructions.append('MOV EAX, {}'.format(ast[1][1]))
        for node in ast[2:]:
            if node[0] == 'OPERATOR':
                if node[1] == '+':
                    instructions.append('ADD EAX, {}'.format(node[2][1]))
                elif node[1] == '-':
                    instructions.append('SUB EAX, {}'.format(node[2][1]))
                elif node[1] == '*':
                    instructions.append('MUL EAX, {}'.format(node[2][1]))
                elif node[1] == '/':
                    instructions.append('DIV EAX, {}'.format(node[2][1]))
            else:
                instructions.append('MOV EBX, {}'.format(node[1][1]))
                instructions.append('ADD EAX, EBX')
    return instructions

source = '(+ (* 4 6) (- 9 3))'
tokens = lexer(source)
ast = parser(tokens)
print(codegen(ast))

The output of this code is:

As you can see, creating a compiler in Python is not a trivial task. It requires a good understanding of language design, lexers, parsers, code generators, and code optimization. However, the rewards are great, and the experience gained is invaluable.