new function to support LSTM Unit

tests/activation.cpp

@@ -1,6 +1,7 @@
 #include <NeuralNetwork/ActivationFunction/Heaviside.h>
 #include <NeuralNetwork/ActivationFunction/Sigmoid.h>
 #include <NeuralNetwork/ActivationFunction/HyperbolicTangent.h>
+#include <NeuralNetwork/ActivationFunction/Linear.h>
 
 #include <iostream>
 #include <cassert>
@@ -26,14 +27,14 @@ int main() {
 
 	{
 		NeuralNetwork::ActivationFunction::Sigmoid s(0.7);
-		assert(s(0.1) > 0.517483);
-		assert(s(0.1) < 0.51750);
+		assert(s(0.1) > 0.482407);
+		assert(s(0.1) < 0.482607);
 
-		assert(s(10) > 0.998989);
-		assert(s(10) < 0.999189);
+		assert(s(10) > 0.000901051);
+		assert(s(10) < 0.000921051);
 	}
 	{
-		NeuralNetwork::ActivationFunction::Sigmoid s(5);
+		NeuralNetwork::ActivationFunction::Sigmoid s(-5);
 		assert(s(0.1) > 0.622359);
 		assert(s(0.1) < 0.622559);
 		
@@ -41,7 +42,7 @@ int main() {
 		assert(s(0.7) < 0.970788);
 	}
 	{
-		NeuralNetwork::ActivationFunction::Sigmoid s(0.7);
+		NeuralNetwork::ActivationFunction::Sigmoid s(-0.7);
 		U.a[0]=0.1;
 		U.a[1]=10;
 		U.v=s(U.v);
@@ -52,8 +53,20 @@ int main() {
 		assert(U.a[1] > 0.998989);
 		assert(U.a[1] < 0.999189);
 	}
+	{
+		NeuralNetwork::ActivationFunction::Linear s(1.0);
+		assert(s(0.5) > 0.4999);
+		assert(s(0.5) < 0.5001);
 
-	std::cout << "OK" << std::endl;
+		assert(s(0.0) == 0.0);
+	}
+	{
+		NeuralNetwork::ActivationFunction::Linear s(0.7);
+		assert(s(0.0) == 0.0);
+
+		assert(s(1.0) > 0.6999);
+		assert(s(1.0) < 0.7001);
+	}
 
 	return 0;
 }