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haloless/calc.py

Created May 15, 2017 03:45
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Usage of ply parser
Raw
calc.py
# -----------------------------------------------------------------------------
# calc.py
#
# A simple calculator with variables -- all in one file.
# -----------------------------------------------------------------------------
import math
import os
tokens = (
'NAME','NUMBER',
'PLUS','MINUS','TIMES','DIVIDE','EQUALS',
'LPAREN','RPAREN',
'COMMA',
)
# Tokens
t_PLUS = r'\+'
t_MINUS = r'-'
t_TIMES = r'\*'
t_DIVIDE = r'/'
t_EQUALS = r'='
t_LPAREN = r'\('
t_RPAREN = r'\)'
t_COMMA = r','
t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
def t_NUMBER(t):
r'\d+'
try:
t.value = int(t.value)
except ValueError:
print("Integer value too large %d", t.value)
t.value = 0
return t
# Ignored characters
t_ignore = " \t"
def t_newline(t):
r'\n+'
t.lexer.lineno += t.value.count("\n")
def t_error(t):
print("Illegal character '%s'" % t.value[0])
t.lexer.skip(1)
# Build the lexer
import ply.lex as lex
lexer = lex.lex()
def test_lexer():
data = '1 , 2,3,,4-1'
lexer.input(data)
for tok in lexer:
print(tok)
# Parsing rules
precedence = (
('left','PLUS','MINUS'),
('left','TIMES','DIVIDE'),
('right','UMINUS'),
)
# dictionary of names
names = {
'pi': math.pi
}
funcs = {
'sin': math.sin,
'cos': math.cos,
'tan': math.tan,
'atan2': math.atan2,
'rad2deg': math.degrees,
'deg2rad': math.radians,
'sinh': math.sinh,
'cosh': math.cosh,
'tanh': math.tanh,
}
# print(names)
# print(funcs)
def p_statement_assign(t):
'statement : NAME EQUALS expression'
names[t[1]] = t[3]
def p_statement_expr(t):
'statement : expression'
print(t[1])
def p_expression_binop(t):
'''expression : expression PLUS expression
| expression MINUS expression
| expression TIMES expression
| expression DIVIDE expression'''
if t[2] == '+' : t[0] = t[1] + t[3]
elif t[2] == '-': t[0] = t[1] - t[3]
elif t[2] == '*': t[0] = t[1] * t[3]
elif t[2] == '/': t[0] = t[1] / t[3]
def p_expression_uminus(t):
'expression : MINUS expression %prec UMINUS'
t[0] = -t[2]
def p_expression_group(t):
'expression : LPAREN expression RPAREN'
t[0] = t[2]
def p_expression_number(t):
'expression : NUMBER'
t[0] = t[1]
def p_expression_name(t):
'expression : NAME'
try:
t[0] = names[t[1]]
except LookupError:
print("Undefined name '%s'" % t[1])
t[0] = 0
def p_expression_func(t):
'expression : NAME LPAREN exprlist RPAREN'
# print(t[1:])
try:
fun = funcs[t[1]]
val = fun(*t[3])
t[0] = val
except LookupError:
print("Undefined func '%s'" % t[1])
t[0] = 0
except TypeError as e:
print("Function arguments no match: %s" % e)
t[0] = 0
except Excpetion as e:
print("Unexpected error: %s" % e)
t[0] = 0
return
def p_exprlist_list(t):
'''exprlist : exprlist COMMA expression'''
# print(t[1:])
t[0] = t[1] + (t[3],)
def p_exprlist_last(t):
'''exprlist : expression'''
# print(t[1:])
t[0] = (t[1],)
def p_error(t):
print("Syntax error at '%s'" % t.value)
import ply.yacc as yacc
parser = yacc.yacc()
def calc_complete(prefix, index):
'''Completor for NAMES and FUNCS'''
words = list(names.keys()) + list(funcs.keys())
matched = [ w for w in words if w.startswith(prefix) ]
try:
return matched[index]
except IndexError:
return None
def main_calc():
try:
import readline
except ImportError:
print('Failed to import readline')
else:
print('Use readline')
readline.parse_and_bind("tab: complete")
readline.set_completer(calc_complete)
while True:
try:
# s = input('calc > ') # Use raw_input on Python 2
s = raw_input('calc > ') # Use raw_input on Python 2
except EOFError:
break
parser.parse(s, lexer=lexer)
if __name__ == '__main__':
# test_lexer()
main_calc()
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