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Author: garyexplains

shunting-yard/calc.py

@@ -0,0 +1,70 @@
+import re
+import sys
+
+def get_precedence(op):
+    precedences = {'+': 1, '-': 1, '*': 2, '/': 2, '^': 3}
+    return precedences.get(op, 0)
+
+def infix_to_postfix(expression):
+    output = []
+    stack = []
+    tokens = tokenize(expression)
+
+    for token in tokens:
+        if token.isnumeric():
+            output.append(token)
+        elif token == '(':
+            stack.append(token)
+        elif token == ')':
+            while stack and stack[-1] != '(':
+                output.append(stack.pop())
+            stack.pop()  # Pop the left parenthesis
+        else:
+            while stack and get_precedence(stack[-1]) >= get_precedence(token):
+                output.append(stack.pop())
+            stack.append(token)
+
+    while stack:
+        output.append(stack.pop())
+
+    return output
+
+def tokenize(expression):
+    # Regular expression pattern for numbers and operators
+    token_pattern = r'\d+|\+|-|\*|/|\(|\)|\^'
+    tokens = re.findall(token_pattern, expression)
+    return tokens
+
+def evaluate_postfix(expression):
+    stack = []
+
+    for token in expression:
+        if token.isdigit():
+            stack.append(int(token))
+        else:
+            b = stack.pop()
+            a = stack.pop()
+            if token == '+':
+                stack.append(a + b)
+            elif token == '-':
+                stack.append(a - b)
+            elif token == '*':
+                stack.append(a * b)
+            elif token == '/':
+                stack.append(a / b)
+            elif token == '^':
+                stack.append(pow(a, b))
+
+    return stack.pop()
+
+while True:
+    if len(sys.argv) != 2:
+        infix_expression = input("")
+    else:
+        infix_expression = sys.argv[1]
+
+    postfix_expression = infix_to_postfix(infix_expression)
+    result = evaluate_postfix(postfix_expression)
+    print(result)
+    if len(sys.argv) == 2:
+        exit(result)