Merge pull request #2312 from peastman/sqrt

Algebraic optimizations

libraries/lepton/src/ParsedExpression.cpp

@@ -271,6 +271,16 @@ ExpressionTreeNode ParsedExpression::substituteSimplerExpression(const Expressio
                 return ExpressionTreeNode(new Operation::MultiplyConstant(-dynamic_cast<const Operation::MultiplyConstant*>(&node.getOperation())->getValue()), children[0].getChildren()[0]);
             break;
         }
+        case Operation::SQRT:
+        {
+            if (children[0].getOperation().getId() == Operation::SQUARE) // sqrt(square(x)) = abs(x)
+                return ExpressionTreeNode(new Operation::Abs(), children[0].getChildren()[0]);
+        }
+        case Operation::SQUARE:
+        {
+            if (children[0].getOperation().getId() == Operation::SQRT) // square(sqrt(x)) = x
+                return children[0].getChildren()[0];
+        }
         default:
         {
             // If operation ID is not one of the above,

tests/TestParser.cpp

@@ -266,6 +266,8 @@ int main() {
         verifyEvaluation("select(x, 1.0, y)", 0.3, 2.0, 1.0);
         verifyEvaluation("select(x, 1.0, y)", 0.0, 2.0, 2.0);
         verifyEvaluation("atan2(x, y)", 3.0, 1.5, std::atan(2.0));
+        verifyEvaluation("sqrt(x^2)", -2.2, 0.0, 2.2);
+        verifyEvaluation("sqrt(x)^2", 2.2, 0.0, 2.2);
         verifyInvalidExpression("1..2");
         verifyInvalidExpression("1*(2+3");
         verifyInvalidExpression("5++4");