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-rw-r--r--lib/python/qmk/math.py33
1 files changed, 33 insertions, 0 deletions
diff --git a/lib/python/qmk/math.py b/lib/python/qmk/math.py
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+"""Parse arbitrary math equations in a safe way.
+
+Gratefully copied from https://stackoverflow.com/a/9558001
+"""
+import ast
+import operator as op
+
+# supported operators
+operators = {ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul, ast.Div: op.truediv, ast.Pow: op.pow, ast.BitXor: op.xor, ast.USub: op.neg}
+
+
+def compute(expr):
+ """Parse a mathematical expression and return the answer.
+
+ >>> compute('2^6')
+ 4
+ >>> compute('2**6')
+ 64
+ >>> compute('1 + 2*3**(4^5) / (6 + -7)')
+ -5.0
+ """
+ return _eval(ast.parse(expr, mode='eval').body)
+
+
+def _eval(node):
+ if isinstance(node, ast.Num): # <number>
+ return node.n
+ elif isinstance(node, ast.BinOp): # <left> <operator> <right>
+ return operators[type(node.op)](_eval(node.left), _eval(node.right))
+ elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
+ return operators[type(node.op)](_eval(node.operand))
+ else:
+ raise TypeError(node)