package net.fortytwo.ripple.libs.math;
import net.fortytwo.flow.Sink;
import net.fortytwo.ripple.RippleException;
import net.fortytwo.ripple.model.ModelConnection;
import net.fortytwo.ripple.model.NumericValue;
import net.fortytwo.ripple.model.PrimitiveStackMapping;
import net.fortytwo.ripple.model.RippleList;
import net.fortytwo.ripple.model.StackMapping;
/**
* A primitive which consumes a number and produces the natural logarithm of the
* number.
*
* @author Joshua Shinavier (http://fortytwo.net)
*/
public class Log extends PrimitiveStackMapping {
private static final String[] IDENTIFIERS = {
MathLibrary.NS_2013_03 + "log",
MathLibrary.NS_2008_08 + "log",
MathLibrary.NS_2007_08 + "log"};
public String[] getIdentifiers() {
return IDENTIFIERS;
}
public Log()
throws RippleException {
super();
}
public Parameter[] getParameters() {
return new Parameter[]{
new Parameter("x", null, true)};
}
public String getComment() {
return "x => natural logarithm of x";
}
public void apply(final RippleList arg,
final Sink<RippleList> solutions,
final ModelConnection mc) throws RippleException {
RippleList stack = arg;
double a;
NumericValue result;
a = mc.toNumericValue(stack.getFirst()).doubleValue();
stack = stack.getRest();
// Apply the function only if it is defined for the given argument.
if (a > 0) {
result = mc.valueOf(Math.log(a));
solutions.put(
stack.push(result));
}
}
@Override
public StackMapping getInverse() throws RippleException {
return MathLibrary.getExpValue();
}
}