haloless · May 15, 2017 03:45 · May 15, 2017
diff --git a/calc.py b/calc.py
@@ -0,0 +1,194 @@
+
+
+# -----------------------------------------------------------------------------
+# 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()
+