Tests for floor() and ceil().

tests/TestParser.cpp

@@ -247,6 +247,8 @@ int main() {
         verifyEvaluation("abs(x-y)", 2.0, 3.0, 1.0);
         verifyEvaluation("delta(x)+3*delta(y-1.5)", 2.0, 1.5, 3.0);
         verifyEvaluation("step(x-3)+y*step(x)", 2.0, 3.0, 3.0);
+        verifyEvaluation("floor(x)", -2.1, 3.0, -3.0);
+        verifyEvaluation("ceil(x)", -2.1, 3.0, -2.0);
         verifyInvalidExpression("1..2");
         verifyInvalidExpression("1*(2+3");
         verifyInvalidExpression("5++4");
@@ -279,6 +281,7 @@ int main() {
         verifyDerivative("min(x, 2*x)", "step(x-2*x)*2+(1-step(x-2*x))*1");
         verifyDerivative("max(5, x^2)", "(1-step(5-x^2))*2*x");
         verifyDerivative("abs(3*x)", "step(3*x)*3+(1-step(3*x))*-3");
+        verifyDerivative("floor(x)+0.5*x*ceil(x)", "0.5*ceil(x)");
         testCustomFunction("custom(x, y)/2", "x*y");
         testCustomFunction("custom(x^2, 1)+custom(2, y-1)", "2*x^2+4*(y-1)");
         cout << Parser::parse("x*x").optimize() << endl;