samer@0: /*
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or 
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  */
samer@0: 
samer@0: package samer.maths;
samer@0: import  samer.core.*;
samer@0: 
samer@0: 
samer@0: public class Linear extends Function
samer@0: {	
samer@0: 	private double	a, b;
samer@0: 
samer@0: 	public Linear() { this( Shell.getDouble("a",1), Shell.getDouble("b",0)); }
samer@0: 	public Linear(double a, double b) { this.a = a; this.b = b; }
samer@0: 
samer@0: 	public double apply(double t) { return a*t+b; }
samer@0: 	public void apply(double [] x) {
samer@0: 		for (int i=0; i<x.length; i++) { x[i]*=a;  x[i]+=b; }
samer@0: 	}
samer@0: 	public void apply(double [] x, double [] y) {
samer@0: 		for (int i=0; i<x.length; i++) y[i]=a*x[i]+b;
samer@0: 	}
samer@0: 	public String format(String arg) { 
samer@0: 		StringBuffer buf=new StringBuffer();
samer@0: 		if (b!=0) {
samer@0: 			buf.append(X.string(b));
samer@0: 			if (a!=0) buf.append(" + ").append(X.string(a)).append(arg);
samer@0: 		} else {
samer@0: 			if (a!=0) buf.append(X.string(a)).append(arg);
samer@0: 			else return "0";
samer@0: 		}
samer@0: 		return buf.toString();
samer@0: 	}
samer@0: 
samer@0: 	public Function derivative() { return new Constant(a); }
samer@0: 	public Function inverse() { return new Linear(-a/b,1/b); }
samer@0: }