From 1f0141ba0c876f85f79424c9de9eb8dd21d58ea0 Mon Sep 17 00:00:00 2001
From: fintarin <valukevichv@gmail.com>
Date: Wed, 12 Jul 2023 17:15:32 +0300
Subject: [PATCH] Implement Pow(Div, Expr)

---
 .../expressions/binary/PowExpression.cpp      | 28 +++++++++++++++++--
 .../expressions/binary/PowExpression.hpp      |  2 ++
 tests/src/expressions/ExpressionTests.cpp     |  7 ++++-
 tests/src/functions/powers/RootTests.cpp      |  2 +-
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/fintamath/expressions/binary/PowExpression.cpp b/src/fintamath/expressions/binary/PowExpression.cpp
index 62ee029cf..dd2841001 100644
--- a/src/fintamath/expressions/binary/PowExpression.cpp
+++ b/src/fintamath/expressions/binary/PowExpression.cpp
@@ -20,9 +20,9 @@ PowExpression::PowExpression(const ArgumentPtr &inLhsChild, const ArgumentPtr &i
 }
 
 std::string PowExpression::toString() const {
-  if (auto val = cast<Rational>(rhsChild)) {
-    const Integer &numerator = val->numerator();
-    const Integer &denominator = val->denominator();
+  if (auto rhsChildRat = cast<Rational>(rhsChild)) {
+    const Integer &numerator = rhsChildRat->numerator();
+    const Integer &denominator = rhsChildRat->denominator();
 
     if (numerator == 1) {
       if (denominator == 2) {
@@ -33,6 +33,12 @@ std::string PowExpression::toString() const {
     }
   }
 
+  if (auto rhsChildExpr = cast<IExpression>(rhsChild); rhsChildExpr && is<Div>(rhsChildExpr->getFunction())) {
+    if (*rhsChildExpr->getChildren().front() == Integer(1)) {
+      return functionToString(Root(), {lhsChild, rhsChildExpr->getChildren().back()});
+    }
+  }
+
   return IBinaryExpression::toString();
 }
 
@@ -219,6 +225,10 @@ ArgumentPtr PowExpression::polynomSimplify(const IFunction & /*func*/, const Arg
     return res;
   }
 
+  if (auto res = divSimplify(lhs, rhs)) {
+    return res;
+  }
+
   return {};
 }
 
@@ -238,6 +248,18 @@ ArgumentPtr PowExpression::mulSimplify(const ArgumentPtr &lhs, const ArgumentPtr
   return res;
 }
 
+ArgumentPtr PowExpression::divSimplify(const ArgumentPtr &lhs, const ArgumentPtr &rhs) {
+  ArgumentPtr res;
+
+  if (auto divExpr = cast<IExpression>(lhs); divExpr && is<Div>(divExpr->getFunction())) {
+    ArgumentPtr numerator = makeExpr(Pow(), divExpr->getChildren().front(), rhs);
+    ArgumentPtr denominator = makeExpr(Pow(), divExpr->getChildren().back(), rhs);
+    res = makeExpr(Div(), numerator, denominator);
+  }
+
+  return res;
+}
+
 ArgumentPtr PowExpression::sumSimplify(const ArgumentPtr &lhs, const ArgumentPtr &rhs) {
   if (const auto rhsInt = cast<Integer>(rhs)) {
     if (auto sumExpr = sumPolynomSimplify(lhs, *rhsInt)) {
diff --git a/src/fintamath/expressions/binary/PowExpression.hpp b/src/fintamath/expressions/binary/PowExpression.hpp
index 4cd075a83..58a835809 100644
--- a/src/fintamath/expressions/binary/PowExpression.hpp
+++ b/src/fintamath/expressions/binary/PowExpression.hpp
@@ -43,6 +43,8 @@ class PowExpression : public IBinaryExpressionCRTP<PowExpression> {
 
   static ArgumentPtr mulSimplify(const ArgumentPtr &lhs, const ArgumentPtr &rhs);
 
+  static ArgumentPtr divSimplify(const ArgumentPtr &lhs, const ArgumentPtr &rhs);
+
   static ArgumentPtr sumSimplify(const ArgumentPtr &lhs, const ArgumentPtr &rhs);
 };
 
diff --git a/tests/src/expressions/ExpressionTests.cpp b/tests/src/expressions/ExpressionTests.cpp
index a9b345481..53f47c1e0 100644
--- a/tests/src/expressions/ExpressionTests.cpp
+++ b/tests/src/expressions/ExpressionTests.cpp
@@ -351,8 +351,13 @@ TEST(ExpressionTests, stringConstructorTest) {
   EXPECT_EQ(Expression("(a+b)*(a+b)*(1/(a+b))").toString(), "a + b");
   EXPECT_EQ(Expression("(x^2+2x+1)/(x+1)").toString(), "x + 1");
 
+  EXPECT_EQ(Expression("(x/y)^2").toString(), "x^2/y^2");
+  EXPECT_EQ(Expression("(x/y)^(1/2)").toString(), "sqrt(x)/sqrt(y)");
+  EXPECT_EQ(Expression("(x/y)^(1/3)").toString(), "root(x, 3)/root(y, 3)");
+  EXPECT_EQ(Expression("(x/y)^x").toString(), "x^x/y^x");
+  EXPECT_EQ(Expression("(x/y)^(1/x)").toString(), "root(x, x)/root(y, x)");
+
   // TODO! implement this
-  // EXPECT_EQ(Expression("(x/y)^2").toString(), "(x^2)/(y^2)");
   // EXPECT_EQ(Expression("sqrt(x^2)").toString(), "abs(x)");
   // EXPECT_EQ(Expression("(x^10)^(1/10))").toString(), "abs(x)");
   // EXPECT_EQ(Expression("(x^3)^(1/3)").toString(), "x");
diff --git a/tests/src/functions/powers/RootTests.cpp b/tests/src/functions/powers/RootTests.cpp
index 367678137..dd97bbc37 100644
--- a/tests/src/functions/powers/RootTests.cpp
+++ b/tests/src/functions/powers/RootTests.cpp
@@ -90,7 +90,7 @@ TEST(RootTests, callTest) {
   EXPECT_EQ(f(Variable("a"), Integer(2))->toString(), "sqrt(a)");
   EXPECT_EQ(f(Variable("a"), Integer(3))->toString(), "root(a, 3)");
   EXPECT_EQ(f(Variable("a"), Integer(123))->toString(), "root(a, 123)");
-  EXPECT_EQ(f(Integer(2), Variable("a"))->toString(), "2^(1/a)");
+  EXPECT_EQ(f(Integer(2), Variable("a"))->toString(), "root(2, a)");
 
   EXPECT_THROW(f(Integer(-10), Integer(2)), UndefinedException);
   EXPECT_THROW(f(Rational(-9289, 10), Rational(2, 3)), UndefinedException);