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 all real square roots of the
* number.
*
* @author Joshua Shinavier (http://fortytwo.net)
*/
public class Sqrt extends PrimitiveStackMapping {
private static final int ARITY = 1;
private static final String[] IDENTIFIERS = {
MathLibrary.NS_2013_03 + "sqrt",
MathLibrary.NS_2008_08 + "sqrt",
MathLibrary.NS_2007_08 + "sqrt"};
private final StackMapping self;
public String[] getIdentifiers() {
return IDENTIFIERS;
}
public Sqrt()
throws RippleException {
super();
this.self = this;
}
public Parameter[] getParameters() {
return new Parameter[]{
new Parameter("x", null, true)};
}
public String getComment() {
return "x => real square root(s) of x";
}
public void apply(final RippleList arg,
final Sink<RippleList> solutions,
final ModelConnection mc) throws RippleException {
RippleList stack = arg;
double a;
a = mc.toNumericValue(stack.getFirst()).doubleValue();
stack = stack.getRest();
// Apply the function only if it is defined for the given argument.
if (a >= 0) {
double d = Math.sqrt(a);
// Yield both square roots.
try {
solutions.put(
stack.push(mc.valueOf(d)));
if (d > 0) {
solutions.put(
stack.push(mc.valueOf(0.0 - d)));
}
} catch (RippleException e) {
// Soft fail
e.logError();
}
}
}
@Override
public StackMapping getInverse() {
return new Square();
}
private class Square implements StackMapping {
public int arity() {
return 1;
}
public StackMapping getInverse() throws RippleException {
return self;
}
public boolean isTransparent() {
return true;
}
public void apply(final RippleList arg,
final Sink<RippleList> solutions,
final ModelConnection mc) throws RippleException {
RippleList stack = arg;
NumericValue a, result;
a = mc.toNumericValue(stack.getFirst());
stack = stack.getRest();
result = a.mul(a);
solutions.put(
stack.push(result));
}
}
}