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Eq.java
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218 lines (193 loc) · 4.98 KB
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package symjava.relational;
import java.util.ArrayList;
import java.util.List;
import symjava.symbolic.Expr;
import symjava.symbolic.utils.Utils;
/**
* An object of Eq represents a equation like
* y = a*x+b
*
*/
public class Eq extends Relation {
Expr[] freeVars; //for example: x in y=a*x+b
Expr[] dependentVars; //for example: y in y=a*x+b
Expr[] params; //paramters in the equation, for example: a, b in y=a*x+b
Expr[] unknowns; //freeVars + dependentVars, for example: x, y in y=a*x+b
/**
* Create an equation like y=... without any parameters
* For example:
* Eq e = new Eq(y, 2*x+1); //y = 2*x+1
*
* @param lhs
* @param rhs
*/
public Eq(Expr lhs, Expr rhs) {
this.lhs = lhs;
this.rhs = rhs;
this.freeVars = Utils.extractSymbols(rhs).toArray(new Expr[0]);
this.params = new Expr[0];
this.dependentVars = Utils.extractSymbols(lhs).toArray(new Expr[0]);
setUnknowns();
}
/**
* Create an equation like y=...
* The free variables are specified on the right hand side (rhs).
* It may contain parameters on the right hand side and the paramters
* can be extracted automatically.
* For example:
* Eq e = Eq(y, a*x+b, new Expr[]{x});
* This will create equation y=a*x+b with
* freeVars = [x]
* params = [a,b]
* dependentVars = [y]
* unkonws = [x,y]
*
* @param lhs
* @param rhs
* @param freeVars
*/
public Eq(Expr lhs, Expr rhs, Expr[] freeVars) {
this.lhs = lhs;
this.rhs = rhs;
this.freeVars = freeVars;
this.dependentVars = Utils.extractSymbols(lhs).toArray(new Expr[0]);
//Find params
List<Expr> list = Utils.extractSymbols(rhs);
List<Expr> paramList = new ArrayList<Expr>();
for(Expr s : list) {
boolean skip = false;
for(int i=0; i<freeVars.length; i++) {
if(s.symEquals(freeVars[i])) {
skip = true;
break;
}
}
if(skip) continue;
paramList.add(s);
}
this.params = paramList.toArray(new Expr[0]);
setUnknowns();
}
public Eq(Expr lhs, Expr rhs, Expr[] freeVars, Expr[] params) {
this.lhs = lhs;
this.rhs = rhs;
this.freeVars = freeVars;
this.params = params;
//Find dependent variables
List<Expr> list = Utils.extractSymbols(lhs, rhs);
List<Expr> depList = new ArrayList<Expr>();
for(Expr s : list) {
boolean skip = false;
for(int i=0; i<freeVars.length; i++) {
if(s.symEquals(freeVars[i])) skip = true;
}
if(skip) continue;
if(params == null) continue;
for(int i=0; i<params.length; i++) {
if(s.symEquals(params[i])) skip = true;
}
if(skip) continue;
depList.add(s);
}
dependentVars = depList.toArray(new Expr[0]);
setUnknowns();
}
/**
*
* @param lhs
* @param rhs
* @param freeVars
* @param params
* @param dependentVars
*/
public Eq(Expr lhs, Expr rhs, Expr[] freeVars, Expr[] params, Expr[] dependentVars) {
this.lhs = lhs;
this.rhs = rhs;
this.freeVars = freeVars;
this.params = params;
this.dependentVars = dependentVars;
setUnknowns();
}
private void setUnknowns() {
this.unknowns = new Expr[freeVars.length + dependentVars.length];
int idx = 0;
for(int i=0; i<freeVars.length; i++) {
unknowns[idx++] = freeVars[i];
}
for(int i=0; i<dependentVars.length; i++) {
unknowns[idx++] = dependentVars[i];
}
}
public static Eq apply(Expr lhs, Expr rhs) {
return new Eq(lhs, rhs);
}
public static Eq apply(Expr lhs, Expr rhs, Expr[] freeVars) {
return new Eq(lhs, rhs, freeVars);
}
public static Eq apply(Expr lhs, Expr rhs, Expr[] freeVars, Expr[] params) {
return new Eq(lhs, rhs, freeVars, params);
}
public static Eq apply(Expr lhs, Expr rhs, Expr[] freeVars, Expr[] params, Expr[] dependentVars) {
return new Eq(lhs, rhs, freeVars, params, dependentVars);
}
public Expr subsLHS(Expr[] from, Expr[] to) {
Expr rlt = lhs;
for(int i=0; i<from.length; i++)
rlt = rlt.subs(from[i], to[i]);
return rlt;
}
public Expr subsRHS(Expr[] from, Expr[] to) {
Expr rlt = rhs;
for(int i=0; i<from.length; i++)
rlt = rlt.subs(from[i], to[i]);
return rlt;
}
public Expr subsLHS(Expr[] from, double[] to) {
Expr rlt = lhs;
for(int i=0; i<from.length; i++)
rlt = rlt.subs(from[i], to[i]);
return rlt;
}
public Expr subsRHS(Expr[] from, double[] to) {
Expr rlt = rhs;
for(int i=0; i<from.length; i++)
rlt = rlt.subs(from[i], to[i]);
return rlt;
}
public Eq subsUnknowns(double[] data) {
return new Eq(
this.subsLHS(unknowns, data),
this.subsRHS(unknowns, data),
this.freeVars,
this.params,
this.dependentVars
);
}
public Eq subsParams(double[] data) {
return new Eq(
this.subsLHS(params, data),
this.subsRHS(params, data),
this.freeVars,
this.params,
this.dependentVars
);
}
public Expr[] getUnknowns() {
return unknowns;
}
public Expr[] getParams() {
return params;
}
public Expr[] getFreeVars () {
return freeVars;
}
public Expr[] getDependentVars() {
return dependentVars;
}
public Expr solve(Expr var) {
return null;
}
public String toString() {
return lhs + " = " + rhs;
}
}