Add custom numeric functions log and exp

There does not seem to be a standard prefix for those, so I am using `<http://qlever.cs.uni-freiburg.de/function#>` for now (abbreviated as prefix `qfn` in the QLever UI).
ad-freiburg · Aug 2, 2023 · 2e0a1d4 · 2e0a1d4
1 parent d50499f
commit 2e0a1d4
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Showing 4 changed files with 59 additions and 2 deletions.
diff --git a/src/engine/sparqlExpressions/NaryExpression.h b/src/engine/sparqlExpressions/NaryExpression.h
@@ -36,6 +36,8 @@ SparqlExpression::Ptr makeRoundExpression(SparqlExpression::Ptr child);
 SparqlExpression::Ptr makeAbsExpression(SparqlExpression::Ptr child);
 SparqlExpression::Ptr makeCeilExpression(SparqlExpression::Ptr child);
 SparqlExpression::Ptr makeFloorExpression(SparqlExpression::Ptr child);
+SparqlExpression::Ptr makeLogExpression(SparqlExpression::Ptr child);
+SparqlExpression::Ptr makeExpExpression(SparqlExpression::Ptr child);
 
 SparqlExpression::Ptr makeDistExpression(SparqlExpression::Ptr child1,
                                          SparqlExpression::Ptr child2);

diff --git a/src/engine/sparqlExpressions/NumericUnaryExpressions.cpp b/src/engine/sparqlExpressions/NumericUnaryExpressions.cpp
@@ -69,6 +69,29 @@ inline const auto floorImpl = []<typename T>(T num) {
 };
 inline const auto floor = makeNumericExpression<decltype(floorImpl)>();
 using FloorExpression = NARY<1, FV<decltype(floor), NumericValueGetter>>;
+
+// Natural Logarithm.
+inline const auto logImpl = []<typename T>(T num) {
+  if constexpr (std::is_floating_point_v<T> || std::is_integral_v<T>) {
+    return num > 0 ? std::log(num) : std::numeric_limits<double>::quiet_NaN();
+  } else {
+    return Id::makeUndefined();
+  }
+};
+inline const auto log = makeNumericExpression<decltype(logImpl)>();
+using LogExpression = NARY<1, FV<decltype(log), NumericValueGetter>>;
+
+// Exponentiation.
+inline const auto expImpl = []<typename T>(T num) {
+  if constexpr (std::is_floating_point_v<T> || std::is_integral_v<T>) {
+    return std::exp(num);
+  } else {
+    return Id::makeUndefined();
+  }
+};
+inline const auto exp = makeNumericExpression<decltype(expImpl)>();
+using ExpExpression = NARY<1, FV<decltype(exp), NumericValueGetter>>;
+
 }  // namespace detail
 
 using namespace detail;
@@ -84,6 +107,12 @@ SparqlExpression::Ptr makeCeilExpression(SparqlExpression::Ptr child) {
 SparqlExpression::Ptr makeFloorExpression(SparqlExpression::Ptr child) {
   return std::make_unique<FloorExpression>(std::move(child));
 }
+SparqlExpression::Ptr makeLogExpression(SparqlExpression::Ptr child) {
+  return std::make_unique<LogExpression>(std::move(child));
+}
+SparqlExpression::Ptr makeExpExpression(SparqlExpression::Ptr child) {
+  return std::make_unique<ExpExpression>(std::move(child));
+}
 
 SparqlExpression::Ptr makeUnaryMinusExpression(SparqlExpression::Ptr child) {
   return std::make_unique<UnaryMinusExpression>(std::move(child));

diff --git a/src/parser/sparqlParser/SparqlQleverVisitor.cpp b/src/parser/sparqlParser/SparqlQleverVisitor.cpp
@@ -72,7 +72,10 @@ ExpressionPtr Visitor::processIriFunctionCall(
 
   constexpr static std::string_view geofPrefix =
       "<http://www.opengis.net/def/function/geosparql/";
-  if (std::string_view iriView = iri; iriView.starts_with(geofPrefix)) {
+  constexpr static std::string_view qfnPrefix =
+      "<http://qlever.cs.uni-freiburg.de/function#";
+  std::string_view iriView = iri;
+  if (iriView.starts_with(geofPrefix)) {
     iriView.remove_prefix(geofPrefix.size());
     AD_CONTRACT_CHECK(iriView.ends_with('>'));
     iriView.remove_suffix(1);
@@ -87,6 +90,17 @@ ExpressionPtr Visitor::processIriFunctionCall(
       checkNumArgs("geof:", iriView, 1);
       return sparqlExpression::makeLatitudeExpression(std::move(argList[0]));
     }
+  } else if (iriView.starts_with(qfnPrefix)) {
+    iriView.remove_prefix(qfnPrefix.size());
+    AD_CONTRACT_CHECK(iriView.ends_with('>'));
+    iriView.remove_suffix(1);
+    if (iriView == "log") {
+      checkNumArgs("qfn:", iriView, 1);
+      return sparqlExpression::makeLogExpression(std::move(argList[0]));
+    } else if (iriView == "exp") {
+      checkNumArgs("qfn:", iriView, 1);
+      return sparqlExpression::makeExpExpression(std::move(argList[0]));
+    }
   }
   reportNotSupported(ctx, "Function \"" + iri + "\" is");
 }

diff --git a/test/SparqlExpressionTest.cpp b/test/SparqlExpressionTest.cpp
@@ -439,7 +439,8 @@ TEST(SparqlExpression, unaryMinus) {
   checkMinus(Strings{"true", "false", "", "<blibb>"}, Ids{U, U, U, U});
 }
 
-TEST(SparqlExpression, ceilFloorAbsRound) {
+// Test the built-in numeric functions (floor, abs, round, ceil).
+TEST(SparqlExpression, builtInNumericFunctions) {
   auto bindUnary = [](auto f) {
     return std::bind_front(testUnaryExpression, f);
   };
@@ -468,6 +469,17 @@ TEST(SparqlExpression, ceilFloorAbsRound) {
   checkRound(input, round);
 }
 
+// Test the custom numeric functions implemented so far (log, exp).
+TEST(SparqlExpression, customNumericFunctions) {
+  auto nan = std::numeric_limits<double>::quiet_NaN();
+  testUnaryExpression(makeLogExpression,
+                      std::vector<Id>{B(false), B(true), I(1), D(exp(1)), U},
+                      std::vector<Id>{D(nan), D(0), D(0), D(1), U});
+  testUnaryExpression(makeExpExpression,
+                      std::vector<Id>{B(false), B(true), I(0), D(1), U},
+                      std::vector<Id>{D(1), D(exp(1)), D(1), D(exp(1)), U});
+}
+
 // ________________________________________________________________________________________
 TEST(SparqlExpression, geoSparqlExpressions) {
   auto checkLat = std::bind_front(testUnaryExpression, &makeLatitudeExpression);