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from dataclasses import dataclass
from enum import Enum, auto
from typing import Any
import sys
class LexError(BaseException):
def __init__(self, message, line):
super().__init__(f"line {line}: {message}")
class TokenType(Enum):
PRINT = auto()
OPEN_PAREN = auto()
CLOSE_PAREN = auto()
EOF = auto()
# literals
INT = auto()
FLOAT = auto()
STRING = auto()
TRUE = auto()
FALSE = auto()
# arithmetic
PLUS = auto()
DASH = auto()
STAR = auto()
SLASH = auto()
# strings
DOUBLE_QUOTE = auto()
# comparison
GREATER = auto()
GREATER_EQUAL = auto()
LESS = auto()
LESS_EQUAL = auto()
EQUAL = auto()
NOT = auto()
AND = auto()
OR = auto()
# flow
IF = auto()
# keywords
DEF = auto()
LAMBDA = auto()
# symbols
SYMBOL = auto()
keywords = {
"print": TokenType.PRINT,
"+": TokenType.PLUS,
"-": TokenType.DASH,
"*": TokenType.STAR,
"/": TokenType.SLASH,
">": TokenType.GREATER,
">=": TokenType.GREATER_EQUAL,
"<": TokenType.LESS,
"<=": TokenType.LESS_EQUAL,
"eq?": TokenType.EQUAL,
"not": TokenType.NOT,
"and": TokenType.AND,
"or": TokenType.OR,
"if": TokenType.IF,
"def": TokenType.DEF,
"lambda": TokenType.LAMBDA }
@dataclass
class Token:
type_: TokenType
text: str
value: Any
line: int
def __str__(self):
return f"{self.type_.name} {self.text} {self.line}"
WHITESPACE = [" ", "\n", "\t"]
SEPARATORS = WHITESPACE + [")"]
DIGITS = list("0123456789")
def lex(data):
start = 0
current = 0
line = 1
end = len(data)
tokens = []
while current < end:
char = data[current]
if char == "\n":
line += 1
if char in WHITESPACE:
current += 1
continue
elif char == "(":
tokens.append(Token(TokenType.OPEN_PAREN, "(", None, line))
elif char == ")":
tokens.append(Token(TokenType.CLOSE_PAREN, ")", None, line))
# numbers
elif char in DIGITS or char == ".":
tok, length = get_number(data[current:], line)
tokens.append(tok)
current += length
# strings
elif char == '"':
tok, length = get_string(data[current+1:], line)
tokens.append(tok)
current += length
# bools
elif char == "#":
tok, length = get_bool(data[current+1:], line)
tokens.append(tok)
current += length
# symbols
else:
tok, length = get_symbol(data[current:], line)
if tok.text in keywords:
tok.type_ = keywords[tok.text]
tokens.append(tok)
current += length
current += 1
tokens.append(Token(TokenType.EOF, "", None, line))
return tokens
def get_number(data, line):
counter = 0
value = ""
is_float = False
char = data[counter]
while char not in SEPARATORS:
if char in DIGITS:
value += char
elif char == ".":
if is_float:
raise LexError("too many '.' in number", line)
is_float = True
value += char
else:
raise Exception(f"invalid number: {value}")
counter += 1
if counter >= len(data):
break
char = data[counter]
if is_float:
return Token(TokenType.FLOAT, value, float(value), line), counter - 1
else:
return Token(TokenType.INT, value, int(value), line), counter - 1
def get_string(data, line):
counter = 0
string = ""
while data[counter] != '"':
string += data[counter]
counter += 1
if counter >= len(data):
raise Exception("couldn't parse string")
return Token(TokenType.STRING, string, string, line), counter + 1
def get_bool(data, line):
if len(data) >= 4 and data[:4] == "true":
return Token(TokenType.TRUE, "#true", True, line), 4
elif len(data) >= 5 and data[:5] == "false":
return Token(TokenType.FALSE, "#false", False, line), 5
else:
raise Exception("couldn't parse boolean")
def get_symbol(data, line):
counter = 0
value = ""
while data[counter] not in SEPARATORS:
value += data[counter]
counter += 1
if counter >= len(data):
break
return Token(TokenType.SYMBOL, value, None, line), counter - 1
def main(data):
try:
tokens = lex(data)
except LexError as error:
print(error)
sys.exit()
for tok in tokens:
print(f"{tok}")
if __name__ == "__main__":
if len(sys.argv) != 2:
print("need a file")
sys.exit()
with open(sys.argv[1], "r") as fil:
data = fil.read()
main(data)
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