Variable.java

package calculator.interpreter;

import java.util.List;
import calculator.interpreter.ast.Node;
import net.sf.etl.parsers.SourceLocation;

/**
 * The variable
 */
public class Variable {
  /** the name of variable to be defined */
  public final String name;
  /** the true value indicate that this name is mutable variable */
  public final boolean isVar;
  /** the true value indicate that is this name has been bound at least once */
  public boolean isBound;
  /** the value of the variable */
  public Object value;
  /** the location where variable is defined */
  public final SourceLocation defineLocation;
  /** the location where variable is set */
  public SourceLocation bindLocation;
  /** the documentation associated with binding (might be null) */
  public final String documentation;
  /** the annotation values (might be null) */
  public final List<AnnotationValue> annotations;

  /**
   *The constructor for the variable
   * 
   * @param previous the previous context (might be null)
   * @param name the name of variable or constant
   * @param isVar if true, the name could be rebound after it was bound
   * @param defineLocation the location where the name was defined
   * @param documentation the documentation associated with the variable
   * @param annotations the list of annotation values
   */
  public Variable(String name, boolean isVar, SourceLocation defineLocation,
      String documentation, List<AnnotationValue> annotations) {
    super();
    this.name = name;
    this.isVar = isVar;
    this.defineLocation = defineLocation;
    this.documentation = documentation;
    this.annotations = annotations;
  }

  /**
   * Get the value bound to the name
   * 
   * @param node the node that requested the bind operation
   * @return the current value of the binding
   */
  public Object get(Node node) {
    if (!isBound) {
      throw new EvalException(node, "The name " + name + " defined at "
          + defineLocation.toShortString() + " has not been bound yet.");
    }
    return value;
  }

  /**
   * Bind the variable with the value
   * 
   * @param location the location of the node that requested the bind operation
   * @param value the value to bind
   * @return the value argument
   */
  public Object bind(SourceLocation location, Object value) {
    if (!isBound) {
      isBound = true;
    } else if (!isVar) {
      throw new EvalException(location,
          "The value has been already bound to constant " + name + " at "
              + bindLocation);
    }
    bindLocation = location;
    this.value = value;
    return value;
  }

  /**
   * @return the help string for the variable
   */
  public String help() {
    StringBuilder b = new StringBuilder();
    b.append("------ ");
    b.append(isVar ? "Varaible " : "Constant ").append(name)
        .append(" ------\n");
    b.append("Defined at ").append(defineLocation.toShortString()).append('\n');
    if (isBound) {
      b.append("Bound at ").append(bindLocation.toShortString()).append(
          " to value ").append(value).append('\n');
    }
    if (documentation == null) {
      b.append("(No documentation defined)\n");
    } else {
      b.append(documentation);
    }
    if (annotations == null || annotations.size() == 0) {
      b.append("(No annotations defined)\n");
    } else {
      for (AnnotationValue v : annotations) {
        b.append(v).append('\n');
      }
    }
    return b.toString();
  }
}