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lexer.py
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lexer.py
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# ------------------------------------------------------------
# Parser for C language subset
# ------------------------------------------------------------
import ply.lex as lex
# List of token names.
tokens = [
"NUMBER",
"LETTER",
"PLUS",
"MINUS",
"TIMES",
"DIVIDE",
"MODULUS",
"AND",
"OR",
"NOT",
"EQUALS",
"LESS",
"GREATER",
"LPAREN",
"RPAREN",
"HEADER",
"ID",
"COMMA",
"SEMICOLON",
"APOST",
"QUOTE",
"LBRACE",
"RBRACE",
"LBRACKET",
"RBRACKET",
"POUND",
"COMMENT",
"COMMENTBLOCK",
"ASSIGN",
"EOF",
]
reserved = {
"int": "INT",
"char": "CHAR",
"float": "FLOAT",
"if": "IF",
"else": "ELSE",
"do": "DO",
"while": "WHILE",
"return": "RETURN",
"void": "VOID",
"define": "DEFINE",
"include": "INCLUDE",
}
tokens += list(reserved.values())
# Regular expression rules for simple tokens
t_PLUS = r"\+"
t_MINUS = r"\-"
t_TIMES = r"\*"
t_DIVIDE = r"\/"
t_MODULUS = r"\%"
t_AND = r"\&\&"
t_OR = r"\|\|"
t_NOT = r"\!"
t_EQUALS = r"\=\="
t_LESS = r"\<"
t_GREATER = r"\>"
t_LPAREN = r"\("
t_RPAREN = r"\)"
t_COMMA = r"\,"
t_SEMICOLON = r"\;"
t_APOST = r"\'"
t_QUOTE = r"\""
t_LBRACE = r"\{"
t_RBRACE = r"\}"
t_LBRACKET = r"\["
t_RBRACKET = r"\]"
t_POUND = r"\#"
t_ASSIGN = r"\="
t_EOF = r"\$"
# A regular expression rule with some action code
def t_COMMENT(t):
r"\/\/.*"
pass
def t_COMMENTBLOCK(t):
r"\/\*(.|\n)*\*\/"
pass
def t_HEADER(t):
r"[a-zA-Z_][a-zA-Z_0-9]*\.h"
return t
def t_ID(t):
r"[a-zA-Z_][a-zA-Z_0-9]*"
t.type = reserved.get(t.value, "ID") # Check for reserved words
return t
def t_NUMBER(t):
r"\d+(\.\d+)?"
t.value = int(t.value)
return t
def t_LETTER(t):
r"\'.\'"
t.value = t.value.replace("'", "")
return t
# Define a rule so we can track line numbers
def t_newline(t):
r"\n+"
t.lexer.lineno += len(t.value)
# A string containing ignored characters (spaces and tabs)
t_ignore = " \t"
# Error handling rule
def t_error(t):
print("Illegal character '%s'" % t.value[0])
t.lexer.skip(1)
# Build the lexer
lexer = lex.lex()
def tokenize(data):
lexer.input(data)