README.md

ToyPL - Compiler Implementation

toy programming language

implementation for a simple compiler, follow the video list on youtube

• 中文版文档
• 问答

source:

• [play list] https://www.youtube.com/channel/UCkyrFlOF7I6U-IMUxum9HrA/videos
• [first video] https://www.youtube.com/watch?v=xqcd6hZD6MY

This document looks messy at the moment. I will revise it with the learning progress.

"premature optimization is the root of all evil".

01 Introduction to the compiler

02 Lexical Analysis

implemented in basic.py

Lexer = code -> lexer -> Tokens

if xxx:
    xxx:
else:
    xxx

The compiler read the source code from a file as a large string shows below

if xxx: \n xxx \n else: xxx

tokenizer -> split the code into a list of token

token: lexical unit => <token-name, attribute-value>

实现目标算术器：

• 1 + 1 - 2 + 4 = 4
• (1 + 1) * 2 = 4
• 1 *+ 1 = Error

03 Syntactic analysis

implemented in grammar.py

Usage

python main.py

tokens -> AST [] -> 递归 -> tree

文法: 语言的规则，toypl

BNF(巴科斯范式) context-free-grammar, 上下文无关文法，可以递归嵌套

Grammar

expr -> term (( PLUS | MINUS ) term)*
term -> factor （( MUL | DIV ) factor)*
factor -> INT | FLOAT
    -> (PLUS | MINUS ) factor
    -> LPAREN expr RPAREN

解释:

• ‘*’ 表示匹配0或者多次
• expr -> term (( PLUS | MINUS ) term)*
  • exp表达式，包括两部分
  • 表达式1：一个term表达式，
  • 表达式2：一个操作(PLUS或者MINUS)在连接一个表达式term
  • 表达式2可以出现0次或者多次
• term -> factor ( MUL | DIV ) factor)*
  • term表达式，包含两部分
  • 表达式：一个factor表达式
  • 表达式2：( MUL | DIV ) factor)*
• factor -> INT | FLOAT -> (PLUS | MINUS ) factor -> LPAREN expr RPAREN
  • 可以有一个int或者float
  • 可以有一个PLUS | MINUS
  • 可以有 '(' + 一个expr表达式 + ')'

04 Interpreter

Principle

• token parser -> RTResult(store the result from interpreter)
• Execution for Interpreter: do correspond operation based on the properties from Ast Node中

For the BinOp, such as 1+1

left node -> 1,
right node -> 1
we execute + operation for left node and right node