From 05912884f9ba98ee5abf720b067dd3095cb0e4eb Mon Sep 17 00:00:00 2001
From: Martin Dobias <wonder.sk@gmail.com>
Date: Tue, 11 Oct 2011 19:46:44 -0300
Subject: [PATCH] Expressions: add exp,ln,log10,log functions (#4365)

---
 src/core/qgsexpression.cpp           | 31 ++++++++++++++++++++++++++++
 tests/src/core/testqgsexpression.cpp |  8 +++++++
 2 files changed, 39 insertions(+)

diff --git a/src/core/qgsexpression.cpp b/src/core/qgsexpression.cpp
index 1b38d94689b..da11095bf83 100644
--- a/src/core/qgsexpression.cpp
+++ b/src/core/qgsexpression.cpp
@@ -208,6 +208,33 @@ static QVariant fcnAtan2( const QVariantList& values, QgsFeature* , QgsExpressio
   double x = getDoubleValue( values.at( 1 ), parent );
   return QVariant( atan2( y, x ) );
 }
+static QVariant fcnExp( const QVariantList& values, QgsFeature* , QgsExpression* parent )
+{
+  double x = getDoubleValue( values.at( 0 ), parent );
+  return QVariant( exp( x ) );
+}
+static QVariant fcnLn( const QVariantList& values, QgsFeature* , QgsExpression* parent )
+{
+  double x = getDoubleValue( values.at( 0 ), parent );
+  if ( x <= 0 )
+    return QVariant();
+  return QVariant( log( x ) );
+}
+static QVariant fcnLog10( const QVariantList& values, QgsFeature* , QgsExpression* parent )
+{
+  double x = getDoubleValue( values.at( 0 ), parent );
+  if ( x <= 0 )
+    return QVariant();
+  return QVariant( log10( x ) );
+}
+static QVariant fcnLog( const QVariantList& values, QgsFeature* , QgsExpression* parent )
+{
+  double b = getDoubleValue( values.at( 0 ), parent );
+  double x = getDoubleValue( values.at( 1 ), parent );
+  if ( x <= 0 || b <= 0 )
+    return QVariant();
+  return QVariant( log( x ) / log( b ) );
+}
 static QVariant fcnToInt( const QVariantList& values, QgsFeature* , QgsExpression* parent )
 {
   return QVariant( getIntValue( values.at( 0 ), parent ) );
@@ -356,6 +383,10 @@ FnDef QgsExpression::BuiltinFunctions[] =
   FnDef( "acos", 1, fcnAcos ),
   FnDef( "atan", 1, fcnAtan ),
   FnDef( "atan2", 2, fcnAtan2 ),
+  FnDef( "exp", 1, fcnExp ),
+  FnDef( "ln", 1, fcnLn ),
+  FnDef( "log10", 1, fcnLog10 ),
+  FnDef( "log", 2, fcnLog ),
   // casts
   FnDef( "toint", 1, fcnToInt ),
   FnDef( "toreal", 1, fcnToReal ),
diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
index ad93427bc2d..6838ffcc84a 100644
--- a/tests/src/core/testqgsexpression.cpp
+++ b/tests/src/core/testqgsexpression.cpp
@@ -192,6 +192,14 @@ class TestQgsExpression: public QObject
       QTest::newRow( "atan 0" ) << "atan(0)" << false << QVariant( 0. );
       QTest::newRow( "atan2(0,1)" ) << "atan2(0,1)" << false << QVariant( 0. );
       QTest::newRow( "atan2(1,0)" ) << "atan2(1,0)" << false << QVariant( M_PI / 2 );
+      QTest::newRow( "exp(0)" ) << "exp(0)" << false << QVariant( 1. );
+      QTest::newRow( "exp(1)" ) << "exp(1)" << false << QVariant( exp(1) );
+      QTest::newRow( "ln(0)" ) << "ln(0)" << false << QVariant();
+      QTest::newRow( "log10(-1)" ) << "log10(-1)" << false << QVariant();
+      QTest::newRow( "ln(1)" ) << "ln(1)" << false << QVariant( log(1) );
+      QTest::newRow( "log10(100)" ) << "log10(100)" << false << QVariant( 2. );
+      QTest::newRow( "log(2,32)" ) << "log(2,32)" << false << QVariant( 5. );
+      QTest::newRow( "log(10,1000)" ) << "log(10,1000)" << false << QVariant( 3. );
 
       // cast functions
       QTest::newRow( "double to int" ) << "toint(3.2)" << false << QVariant( 3 );