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/*
* Made with all the love in the world
* by scireum in Remshalden, Germany
*
* Copyright by scireum GmbH
* http://www.scireum.de - [email protected]
*/
package parsii.eval;
/**
* Represents a variable which binds a value to a name.
*
* A variable is resolved or created using a {@link Scope}. This ensures that the same name always resolves to the
* same variable. In contrast to using a Map, reading and writing a variable can be much faster, as it only needs
* to be resolved once. Reading and writing it, is basically as cheap as a field access.
*
* A variable can be made constant, which will fail all further attempts to change it.
*/
public class Variable {
private double value = 0d;
private String name;
private boolean constant = false;
/**
* Creates a new variable.
*
* Variables should only be created by their surrounding {@link Scope} so that all following look-ups
* yield the same variable.
*
* @param name the name of the variable
*/
protected Variable(String name) {
this.name = name;
}
/**
* Sets the value if the variable.
*
* @param value the new value of the variable
* @throws IllegalStateException if the variable is constant
*/
public void setValue(double value) {
if (constant) {
throw new IllegalStateException(String.format("%s is constant!", name));
}
this.value = value;
}
/**
* Sets the given value and marks it as constant.
*
* @param value the new (and final) value of this variable
*/
public void makeConstant(double value) {
setValue(value);
this.constant = true;
}
/**
* Returns the value previously set.
*
* @return the value previously set or 0 if the variable is not written yet
*/
public double getValue() {
return value;
}
@Override
public String toString() {
return name + ": " + value;
}
/**
* Returns the name of the variable.
*
* @return the name of this variable
*/
public String getName() {
return name;
}
/**
* Determines if this variable is constant.
*
* @return true if this variable cannot be modified anymore, false otherwise
*/
public boolean isConstant() {
return constant;
}
/**
* Sets the value and returns this.
*
* @param value the new value of this variable
* @return this for fluent method calls
*/
public Variable withValue(double value) {
setValue(value);
return this;
}
}