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Fem: [skip ci] use ply parser instead of insecure eval() function (no…
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# *************************************************************************** | ||
# * Copyright (c) 2020 Werner Mayer <wmayer[at]users.sourceforge.net> * | ||
# * * | ||
# * This program is free software; you can redistribute it and/or modify * | ||
# * it under the terms of the GNU Lesser General Public License (LGPL) * | ||
# * as published by the Free Software Foundation; either version 2 of * | ||
# * the License, or (at your option) any later version. * | ||
# * for detail see the LICENCE text file. * | ||
# * * | ||
# * This program is distributed in the hope that it will be useful, * | ||
# * but WITHOUT ANY WARRANTY; without even the implied warranty of * | ||
# * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * | ||
# * GNU Library General Public License for more details. * | ||
# * * | ||
# * You should have received a copy of the GNU Library General Public * | ||
# * License along with this program; if not, write to the Free Software * | ||
# * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 * | ||
# * USA * | ||
# * * | ||
# *************************************************************************** | ||
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__title__ = "FEM Utilities" | ||
__author__ = "Werner Mayer" | ||
__url__ = "http://www.freecadweb.org" | ||
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tokens = ( | ||
'NAME','FLOAT','INT', | ||
'PLUS','MINUS','TIMES','DIVIDE','EQUALS', | ||
'LPAREN','RPAREN','COMMENT', | ||
) | ||
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# Tokens | ||
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t_PLUS = r'\+' | ||
t_MINUS = r'-' | ||
t_TIMES = r'\*' | ||
t_DIVIDE = r'/' | ||
t_EQUALS = r'=' | ||
t_LPAREN = r'\(' | ||
t_RPAREN = r'\)' | ||
t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*' | ||
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def t_FLOAT(t): | ||
r'\d+\.(\d+)?([eE][-+]?\d+)?' | ||
t.value = float(t.value) | ||
return t | ||
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def t_INT(t): | ||
r'\d+' | ||
t.value = int(t.value) | ||
return t | ||
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# Ignored characters | ||
t_ignore = " \t" | ||
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def t_COMMENT(t): | ||
r'\#.*' | ||
pass | ||
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def t_newline(t): | ||
r'\n+' | ||
t.lexer.lineno += t.value.count("\n") | ||
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def t_error(t): | ||
print("Illegal character '%s'" % t.value[0]) | ||
t.lexer.skip(1) | ||
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# Build the lexer | ||
import ply.lex as lex | ||
lex.lex() | ||
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# Precedence rules for the arithmetic operators | ||
precedence = ( | ||
('left','PLUS','MINUS'), | ||
('left','TIMES','DIVIDE'), | ||
('right','UMINUS'), | ||
) | ||
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# dictionary of names (for storing variables) | ||
names = { } | ||
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def p_statement_assign(p): | ||
'statement : NAME EQUALS expression' | ||
names[p[1]] = p[3] | ||
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def p_statement_expr(p): | ||
'statement : expression' | ||
print(p[1]) | ||
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def p_expression_binop(p): | ||
'''expression : expression PLUS expression | ||
| expression MINUS expression | ||
| expression TIMES expression | ||
| expression DIVIDE expression''' | ||
if p[2] == '+' : p[0] = p[1] + p[3] | ||
elif p[2] == '-': p[0] = p[1] - p[3] | ||
elif p[2] == '*': p[0] = p[1] * p[3] | ||
elif p[2] == '/': p[0] = p[1] / p[3] | ||
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def p_expression_uminus(p): | ||
'expression : MINUS expression %prec UMINUS' | ||
p[0] = -p[2] | ||
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def p_expression_group(p): | ||
'expression : LPAREN expression RPAREN' | ||
p[0] = p[2] | ||
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def p_expression_float(p): | ||
'expression : FLOAT' | ||
p[0] = p[1] | ||
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def p_expression_int(p): | ||
'expression : INT' | ||
p[0] = p[1] | ||
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def p_expression_name(p): | ||
'expression : NAME' | ||
try: | ||
p[0] = names[p[1]] | ||
except LookupError: | ||
print("Undefined name '%s'" % p[1]) | ||
p[0] = 0 | ||
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def p_error(p): | ||
print("Syntax error at '%s'" % p.value) | ||
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import ply.yacc as yacc | ||
yacc.yacc() |