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-rw-r--r--third_party/python/ply/example/calceof/calc.py132
1 files changed, 132 insertions, 0 deletions
diff --git a/third_party/python/ply/example/calceof/calc.py b/third_party/python/ply/example/calceof/calc.py
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+++ b/third_party/python/ply/example/calceof/calc.py
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+# -----------------------------------------------------------------------------
+# calc.py
+#
+# A simple calculator with variables. Asks the user for more input and
+# demonstrates the use of the t_eof() rule.
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0, "../..")
+
+if sys.version_info[0] >= 3:
+ raw_input = input
+
+tokens = (
+ 'NAME', 'NUMBER',
+)
+
+literals = ['=', '+', '-', '*', '/', '(', ')']
+
+# Tokens
+
+t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
+
+
+def t_NUMBER(t):
+ r'\d+'
+ t.value = int(t.value)
+ return t
+
+t_ignore = " \t"
+
+
+def t_newline(t):
+ r'\n+'
+ t.lexer.lineno += t.value.count("\n")
+
+
+def t_eof(t):
+ more = raw_input('... ')
+ if more:
+ t.lexer.input(more + '\n')
+ return t.lexer.token()
+ else:
+ return None
+
+
+def t_error(t):
+ print("Illegal character '%s'" % t.value[0])
+ t.lexer.skip(1)
+
+# Build the lexer
+import ply.lex as lex
+lex.lex()
+
+# Parsing rules
+
+precedence = (
+ ('left', '+', '-'),
+ ('left', '*', '/'),
+ ('right', 'UMINUS'),
+)
+
+# dictionary of names
+names = {}
+
+
+def p_statement_assign(p):
+ 'statement : NAME "=" expression'
+ names[p[1]] = p[3]
+
+
+def p_statement_expr(p):
+ 'statement : expression'
+ print(p[1])
+
+
+def p_expression_binop(p):
+ '''expression : expression '+' expression
+ | expression '-' expression
+ | expression '*' expression
+ | expression '/' 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]
+
+
+def p_expression_uminus(p):
+ "expression : '-' expression %prec UMINUS"
+ p[0] = -p[2]
+
+
+def p_expression_group(p):
+ "expression : '(' expression ')'"
+ p[0] = p[2]
+
+
+def p_expression_number(p):
+ "expression : NUMBER"
+ p[0] = p[1]
+
+
+def p_expression_name(p):
+ "expression : NAME"
+ try:
+ p[0] = names[p[1]]
+ except LookupError:
+ print("Undefined name '%s'" % p[1])
+ p[0] = 0
+
+
+def p_error(p):
+ if p:
+ print("Syntax error at '%s'" % p.value)
+ else:
+ print("Syntax error at EOF")
+
+import ply.yacc as yacc
+yacc.yacc()
+
+while 1:
+ try:
+ s = raw_input('calc > ')
+ except EOFError:
+ break
+ if not s:
+ continue
+ yacc.parse(s + '\n')