Java Code Examples for com.google.javascript.rhino.jstype.TernaryValue#UNKNOWN

/**
 * Copied from Rhino's ScriptRuntime
 */
static TernaryValue isStrWhiteSpaceChar(int c) {
  switch (c) {
    case '\u000B': // <VT>
      return TernaryValue.UNKNOWN;  // IE says "no", EcmaScript says "yes"
    case ' ': // <SP>
    case '\n': // <LF>
    case '\r': // <CR>
    case '\t': // <TAB>
    case '\u00A0': // <NBSP>
    case '\u000C': // <FF>
    case '\u2028': // <LS>
    case '\u2029': // <PS>
    case '\uFEFF': // <BOM>
      return TernaryValue.TRUE;
    default:
      return (Character.getType(c) == Character.SPACE_SEPARATOR)
          ? TernaryValue.TRUE : TernaryValue.FALSE;
  }
}
 

/**
 * Copied from Rhino's ScriptRuntime
 */
public static TernaryValue isStrWhiteSpaceChar(int c) {
  switch (c) {
    case '\u000B': // <VT>
      return TernaryValue.UNKNOWN;  // IE says "no", ECMAScript says "yes"
    case ' ': // <SP>
    case '\n': // <LF>
    case '\r': // <CR>
    case '\t': // <TAB>
    case '\u00A0': // <NBSP>
    case '\u000C': // <FF>
    case '\u2028': // <LS>
    case '\u2029': // <PS>
    case '\uFEFF': // <BOM>
      return TernaryValue.TRUE;
    default:
      return (Character.getType(c) == Character.SPACE_SEPARATOR)
          ? TernaryValue.TRUE : TernaryValue.FALSE;
  }
}
 

/**
 * Copied from Rhino's ScriptRuntime
 */
public static TernaryValue isStrWhiteSpaceChar(int c) {
  switch (c) {
    case '\u000B': // <VT>
      return TernaryValue.UNKNOWN;  // IE says "no", ECMAScript says "yes"
    case ' ': // <SP>
    case '\n': // <LF>
    case '\r': // <CR>
    case '\t': // <TAB>
    case '\u00A0': // <NBSP>
    case '\u000C': // <FF>
    case '\u2028': // <LS>
    case '\u2029': // <PS>
    case '\uFEFF': // <BOM>
      return TernaryValue.TRUE;
    default:
      return (Character.getType(c) == Character.SPACE_SEPARATOR)
          ? TernaryValue.TRUE : TernaryValue.FALSE;
  }
}
 

/**
 * Copied from Rhino's ScriptRuntime
 */
public static TernaryValue isStrWhiteSpaceChar(int c) {
  switch (c) {
    case '\u000B': // <VT>
      return TernaryValue.UNKNOWN;  // IE says "no", ECMAScript says "yes"
    case ' ': // <SP>
    case '\n': // <LF>
    case '\r': // <CR>
    case '\t': // <TAB>
    case '\u00A0': // <NBSP>
    case '\u000C': // <FF>
    case '\u2028': // <LS>
    case '\u2029': // <PS>
    case '\uFEFF': // <BOM>
      return TernaryValue.TRUE;
    default:
      return (Character.getType(c) == Character.SPACE_SEPARATOR)
          ? TernaryValue.TRUE : TernaryValue.FALSE;
  }
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
    case Token.STRING_KEY:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
      return "false";

    case Token.TRUE:
      return "true";

    case Token.NULL:
      return "null";

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Gets the value of a node as a Number, or null if it cannot be converted.
 * When it returns a non-null Double, this method effectively emulates the
 * <code>Number()</code> JavaScript cast function.
 */
static Double getNumberValue(Node n) {
  switch (n.getType()) {
    case Token.TRUE:
      return 1.0;

    case Token.FALSE:
    case Token.NULL:
      return 0.0;

    case Token.NUMBER:
      return n.getDouble();

    case Token.VOID:
      if (mayHaveSideEffects(n.getFirstChild())) {
        return null;
      } else {
        return Double.NaN;
      }

    case Token.NAME:
      // Check for known constants
      String name = n.getString();
      if (name.equals("undefined")) {
        return Double.NaN;
      }
      if (name.equals("NaN")) {
        return Double.NaN;
      }
      if (name.equals("Infinity")) {
        return Double.POSITIVE_INFINITY;
      }
      return null;

    case Token.NEG:
      if (n.getChildCount() == 1 && n.getFirstChild().isName()
          && n.getFirstChild().getString().equals("Infinity")) {
        return Double.NEGATIVE_INFINITY;
      }
      return null;

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? 0.0 : 1.0; // reversed.
      }
      break;

    case Token.STRING:
      return getStringNumberValue(n.getString());

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      String value = getStringValue(n);
      return value != null ? getStringNumberValue(value) : null;
  }

  return null;
}
 

private Node tryFoldUnaryOperator(Node n) {
  Preconditions.checkState(n.hasOneChild());

  Node left = n.getFirstChild();
  Node parent = n.getParent();

  if (left == null) {
    return n;
  }

  TernaryValue leftVal = NodeUtil.getPureBooleanValue(left);
  if (leftVal == TernaryValue.UNKNOWN) {
    return n;
  }

  switch (n.getType()) {
    case Token.NOT:
      // Don't fold !0 and !1 back to false.
      if (late && left.isNumber()) {
        double numValue = left.getDouble();
        if (numValue == 0 || numValue == 1) {
          return n;
        }
      }
      Node replacementNode = NodeUtil.booleanNode(!leftVal.toBoolean(true));
      parent.replaceChild(n, replacementNode);
      reportCodeChange();
      return replacementNode;
    case Token.POS:
      if (NodeUtil.isNumericResult(left)) {
        // POS does nothing to numeric values.
        parent.replaceChild(n, left.detachFromParent());
        reportCodeChange();
        return left;
      }
      return n;
    case Token.NEG:
      if (left.isName()) {
        if (left.getString().equals("Infinity")) {
          // "-Infinity" is valid and a literal, don't modify it.
          return n;
        } else if (left.getString().equals("NaN")) {
          // "-NaN" is "NaN".
          n.removeChild(left);
          parent.replaceChild(n, left);
          reportCodeChange();
          return left;
        }
      }

      if (left.isNumber()) {
        double negNum = -left.getDouble();

        Node negNumNode = IR.number(negNum);
        parent.replaceChild(n, negNumNode);
        reportCodeChange();
        return negNumNode;
      } else {
        // left is not a number node, so do not replace, but warn the
        // user because they can't be doing anything good
        report(NEGATING_A_NON_NUMBER_ERROR, left);
        return n;
      }
    case Token.BITNOT:
      try {
        double val = left.getDouble();
        if (val >= Integer.MIN_VALUE && val <= Integer.MAX_VALUE) {
          int intVal = (int) val;
          if (intVal == val) {
            Node notIntValNode = IR.number(~intVal);
            parent.replaceChild(n, notIntValNode);
            reportCodeChange();
            return notIntValNode;
          } else {
            report(FRACTIONAL_BITWISE_OPERAND, left);
            return n;
          }
        } else {
          report(BITWISE_OPERAND_OUT_OF_RANGE, left);
          return n;
        }
      } catch (UnsupportedOperationException ex) {
        // left is not a number node, so do not replace, but warn the
        // user because they can't be doing anything good
        report(NEGATING_A_NON_NUMBER_ERROR, left);
        return n;
      }
      default:
        return n;
  }
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
    case Token.STRING_KEY:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
      return "false";

    case Token.TRUE:
      return "true";

    case Token.NULL:
      return "null";

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
    case Token.STRING_KEY:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
      return "false";

    case Token.TRUE:
      return "true";

    case Token.NULL:
      return "null";

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
    case Token.TRUE:
    case Token.NULL:
      return Node.tokenToName(n.getType());

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Gets the value of a node as a Number, or null if it cannot be converted.
 * When it returns a non-null Double, this method effectively emulates the
 * <code>Number()</code> JavaScript cast function.
 */
static Double getNumberValue(Node n) {
  switch (n.getType()) {
    case Token.TRUE:
      return 1.0;

    case Token.FALSE:
    case Token.NULL:
      return 0.0;

    case Token.NUMBER:
      return n.getDouble();

    case Token.VOID:
      if (mayHaveSideEffects(n.getFirstChild())) {
        return null;
      } else {
        return Double.NaN;
      }

    case Token.NAME:
      // Check for known constants
      String name = n.getString();
      if (name.equals("undefined")) {
        return Double.NaN;
      }
      if (name.equals("NaN")) {
        return Double.NaN;
      }
      if (name.equals("Infinity")) {
        return Double.POSITIVE_INFINITY;
      }
      return null;

    case Token.NEG:
      if (n.getChildCount() == 1 && n.getFirstChild().getType() == Token.NAME
          && n.getFirstChild().getString().equals("Infinity")) {
        return Double.NEGATIVE_INFINITY;
      }
      return null;

    case Token.NOT:
      TernaryValue child = getBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? 0.0 : 1.0; // reversed.
      }
      break;

    case Token.STRING:
      return getStringNumberValue(n.getString());

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      String value = getStringValue(n);
      return value != null ? getStringNumberValue(value) : null;
  }

  return null;
}
 

/**
 * Gets the boolean value of a node that represents a literal. This method
 * effectively emulates the <code>Boolean()</code> JavaScript cast function
 * except it return UNKNOWN for known values with side-effects, use
 * getExpressionBooleanValue if you don't care about side-effects.
 */
static TernaryValue getPureBooleanValue(Node n) {
  switch (n.getType()) {
    case Token.STRING:
      return TernaryValue.forBoolean(n.getString().length() > 0);

    case Token.NUMBER:
      return TernaryValue.forBoolean(n.getDouble() != 0);

    case Token.NOT:
      return getPureBooleanValue(n.getLastChild()).not();

    case Token.NULL:
    case Token.FALSE:
      return TernaryValue.FALSE;

    case Token.VOID:
      if (!mayHaveSideEffects(n.getFirstChild())) {
        return TernaryValue.FALSE;
      }
      break;

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "NaN".equals(name)) {
        // We assume here that programs don't change the value of the keyword
        // undefined to something other than the value undefined.
        return TernaryValue.FALSE;
      } else if ("Infinity".equals(name)) {
        return TernaryValue.TRUE;
      }
      break;

    case Token.TRUE:
    case Token.REGEXP:
      return TernaryValue.TRUE;

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      if (!mayHaveSideEffects(n)) {
        return TernaryValue.TRUE;
      }
      break;
  }

  return TernaryValue.UNKNOWN;
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
    case Token.STRING_KEY:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
      return "false";

    case Token.TRUE:
      return "true";

    case Token.NULL:
      return "null";

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Try to fold a AND/OR node.
 */
private Node tryFoldAndOr(Node n, Node left, Node right) {
  Node parent = n.getParent();

  Node result = null;

  int type = n.getType();

  TernaryValue leftVal = NodeUtil.getBooleanValue(left);

  if (leftVal != TernaryValue.UNKNOWN) {
    boolean lval = leftVal.toBoolean(true);

    // (TRUE || x) => TRUE (also, (3 || x) => 3)
    // (FALSE && x) => FALSE
    if (lval && type == Token.OR ||
        !lval && type == Token.AND) {
      result = left;

    } else {
      // (FALSE || x) => x
      // (TRUE && x) => x
      result = right;
    }
  } else {
    TernaryValue rightVal = NodeUtil.getBooleanValue(right);
    if (rightVal != TernaryValue.UNKNOWN) {

    // Note: We cannot always fold when the constant is on the
    // right, because the typed value of the expression will depend
    // on the type of the constant on the right, even if the boolean
    // equivalent of the value does not. Specifically, in "a = x ||
    // 0", a will be numeric 0 if x is undefined (and hence is
    // e.g. a valid array index). However, it is safe to fold
    // e.g. "if (x || true)" because 'if' doesn't care if the
    // expression is 'true' or '3'.
    int pt = parent.getType();
    if (pt == Token.IF || pt == Token.WHILE || pt == Token.DO ||
        (pt == Token.FOR && NodeUtil.getConditionExpression(parent) == n) ||
        (pt == Token.HOOK && parent.getFirstChild() == n)) {
      boolean rval = rightVal.toBoolean(true);

      // (x || FALSE) => x
      // (x && TRUE) => x
      if (type == Token.OR && !rval ||
          type == Token.AND && rval) {
        result = left;
      } else {
        // If x has no side-effects:
        //   (x || TRUE) => TRUE
        //   (x && FALSE) => FALSE
        if (!NodeUtil.mayHaveSideEffects(left)) {
          result = right;
        }
      }
      }
    }
  }

  // Note: The parser parses 'x && FALSE && y' as 'x && (FALSE && y)', so
  // there is not much need to worry about const values on left's
  // right child.

  if (result != null) {
    // Fold it!
    n.removeChild(result);
    parent.replaceChild(n, result);
    reportCodeChange();

    return result;
  } else {
    return n;
  }
}
 

/**
 * Remove useless switches and cases.
 */
private Node tryOptimizeSwitch(Node n) {
  Preconditions.checkState(n.isSwitch());

  Node defaultCase = tryOptimizeDefaultCase(n);

  // Removing cases when there exists a default case is not safe.
  if (defaultCase == null) {
    Node cond = n.getFirstChild(), prev = null, next = null, cur;

    for (cur = cond.getNext(); cur != null; cur = next) {
      next = cur.getNext();
      if (!mayHaveSideEffects(cur.getFirstChild()) &&
          isUselessCase(cur, prev)) {
        removeCase(n, cur);
      } else {
        prev = cur;
      }
    }

    // Optimize switches with constant condition
    if (NodeUtil.isLiteralValue(cond, false)) {
      Node caseLabel;
      TernaryValue caseMatches = TernaryValue.TRUE;
      // Remove cases until you find one that may match
      for (cur = cond.getNext(); cur != null; cur = next) {
        next = cur.getNext();
        caseLabel = cur.getFirstChild();
        caseMatches = PeepholeFoldConstants.evaluateComparison(
            Token.SHEQ, cond, caseLabel);
        if (caseMatches == TernaryValue.TRUE) {
          break;
        } else if (caseMatches == TernaryValue.UNKNOWN) {
          break;
        } else {
          removeCase(n, cur);
        }
      }
      if (caseMatches != TernaryValue.UNKNOWN) {
        Node block, lastStm;
        // Skip cases until you find one whose last stm is a break
        while (cur != null) {
          block = cur.getLastChild();
          lastStm = block.getLastChild();
          cur = cur.getNext();
          if (lastStm != null && lastStm.isBreak()) {
            block.removeChild(lastStm);
            reportCodeChange();
            break;
          }
        }
        // Remove any remaining cases
        for (; cur != null; cur = next) {
          next = cur.getNext();
          removeCase(n, cur);
        }
        // If there is one case left, we may be able to fold it
        cur = cond.getNext();
        if (cur != null && cur.getNext() == null) {
          block = cur.getLastChild();
          if (!(NodeUtil.containsType(block, Token.BREAK,
              NodeUtil.MATCH_NOT_FUNCTION))) {
            cur.removeChild(block);
            n.getParent().replaceChild(n, block);
            reportCodeChange();
            return block;
          }
        }
      }
    }
  }

  // Remove the switch if there are no remaining cases.
  if (n.hasOneChild()) {
    Node condition = n.removeFirstChild();
    Node replacement = IR.exprResult(condition).srcref(n);
    n.getParent().replaceChild(n, replacement);
    reportCodeChange();
    return replacement;
  }

  return null;
}
 

/**
 * Gets the boolean value of a node that represents a literal. This method
 * effectively emulates the <code>Boolean()</code> JavaScript cast function
 * except it return UNKNOWN for known values with side-effects, use
 * getExpressionBooleanValue if you don't care about side-effects.
 */
static TernaryValue getPureBooleanValue(Node n) {
  switch (n.getType()) {
    case Token.STRING:
      return TernaryValue.forBoolean(n.getString().length() > 0);

    case Token.NUMBER:
      return TernaryValue.forBoolean(n.getDouble() != 0);

    case Token.NOT:
      return getPureBooleanValue(n.getLastChild()).not();

    case Token.NULL:
    case Token.FALSE:
      return TernaryValue.FALSE;

    case Token.VOID:
      if (!mayHaveSideEffects(n.getFirstChild())) {
        return TernaryValue.FALSE;
      }
      break;

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "NaN".equals(name)) {
        // We assume here that programs don't change the value of the keyword
        // undefined to something other than the value undefined.
        return TernaryValue.FALSE;
      } else if ("Infinity".equals(name)) {
        return TernaryValue.TRUE;
      }
      break;

    case Token.TRUE:
    case Token.REGEXP:
      return TernaryValue.TRUE;

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      if (!mayHaveSideEffects(n)) {
        return TernaryValue.TRUE;
      }
      break;
  }

  return TernaryValue.UNKNOWN;
}
 

/**
 * Gets the value of a node as a String, or null if it cannot be converted.
 * When it returns a non-null String, this method effectively emulates the
 * <code>String()</code> JavaScript cast function.
 */
static String getStringValue(Node n) {
  // TODO(user): regex literals as well.
  switch (n.getType()) {
    case Token.STRING:
    case Token.STRING_KEY:
      return n.getString();

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "Infinity".equals(name)
          || "NaN".equals(name)) {
        return name;
      }
      break;

    case Token.NUMBER:
      return getStringValue(n.getDouble());

    case Token.FALSE:
      return "false";

    case Token.TRUE:
      return "true";

    case Token.NULL:
      return "null";

    case Token.VOID:
      return "undefined";

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? "false" : "true"; // reversed.
      }
      break;

    case Token.ARRAYLIT:
      return arrayToString(n);

    case Token.OBJECTLIT:
      return "[object Object]";
  }
  return null;
}
 

/**
 * Gets the value of a node as a Number, or null if it cannot be converted.
 * When it returns a non-null Double, this method effectively emulates the
 * <code>Number()</code> JavaScript cast function.
 */
static Double getNumberValue(Node n) {
  switch (n.getType()) {
    case Token.TRUE:
      return 1.0;

    case Token.FALSE:
    case Token.NULL:
      return 0.0;

    case Token.NUMBER:
      return n.getDouble();

    case Token.VOID:
      if (mayHaveSideEffects(n.getFirstChild())) {
        return null;
      } else {
        return Double.NaN;
      }

    case Token.NAME:
      // Check for known constants
      String name = n.getString();
      if (name.equals("undefined")) {
        return Double.NaN;
      }
      if (name.equals("NaN")) {
        return Double.NaN;
      }
      if (name.equals("Infinity")) {
        return Double.POSITIVE_INFINITY;
      }
      return null;

    case Token.NEG:
      if (n.getChildCount() == 1 && n.getFirstChild().getType() == Token.NAME
          && n.getFirstChild().getString().equals("Infinity")) {
        return Double.NEGATIVE_INFINITY;
      }
      return null;

    case Token.NOT:
      TernaryValue child = getPureBooleanValue(n.getFirstChild());
      if (child != TernaryValue.UNKNOWN) {
        return child.toBoolean(true) ? 0.0 : 1.0; // reversed.
      }
      break;

    case Token.STRING:
      return getStringNumberValue(n.getString());

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      String value = getStringValue(n);
      return value != null ? getStringNumberValue(value) : null;
  }

  return null;
}
 

/**
 * Gets the boolean value of a node that represents a literal. This method
 * effectively emulates the <code>Boolean()</code> JavaScript cast function
 * except it return UNKNOWN for known values with side-effects, use
 * getExpressionBooleanValue if you don't care about side-effects.
 */
static TernaryValue getPureBooleanValue(Node n) {
  switch (n.getType()) {
    case Token.STRING:
      return TernaryValue.forBoolean(n.getString().length() > 0);

    case Token.NUMBER:
      return TernaryValue.forBoolean(n.getDouble() != 0);

    case Token.NOT:
      return getPureBooleanValue(n.getLastChild()).not();

    case Token.NULL:
    case Token.FALSE:
    case Token.VOID:
      return TernaryValue.FALSE;

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "NaN".equals(name)) {
        // We assume here that programs don't change the value of the keyword
        // undefined to something other than the value undefined.
        return TernaryValue.FALSE;
      } else if ("Infinity".equals(name)) {
        return TernaryValue.TRUE;
      }
      break;

    case Token.TRUE:
    case Token.REGEXP:
      return TernaryValue.TRUE;

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      if (!mayHaveSideEffects(n)) {
        return TernaryValue.TRUE;
      }
  }

  return TernaryValue.UNKNOWN;
}
 

/**
 * Gets the boolean value of a node that represents a literal. This method
 * effectively emulates the <code>Boolean()</code> JavaScript cast function
 * except it return UNKNOWN for known values with side-effects, use
 * getExpressionBooleanValue if you don't care about side-effects.
 */
static TernaryValue getPureBooleanValue(Node n) {
  switch (n.getType()) {
    case Token.STRING:
      return TernaryValue.forBoolean(n.getString().length() > 0);

    case Token.NUMBER:
      return TernaryValue.forBoolean(n.getDouble() != 0);

    case Token.NOT:
      return getPureBooleanValue(n.getLastChild()).not();

    case Token.NULL:
    case Token.FALSE:
      return TernaryValue.FALSE;

    case Token.VOID:
      if (!mayHaveSideEffects(n.getFirstChild())) {
        return TernaryValue.FALSE;
      }
      break;

    case Token.NAME:
      String name = n.getString();
      if ("undefined".equals(name)
          || "NaN".equals(name)) {
        // We assume here that programs don't change the value of the keyword
        // undefined to something other than the value undefined.
        return TernaryValue.FALSE;
      } else if ("Infinity".equals(name)) {
        return TernaryValue.TRUE;
      }
      break;

    case Token.TRUE:
    case Token.REGEXP:
      return TernaryValue.TRUE;

    case Token.ARRAYLIT:
    case Token.OBJECTLIT:
      if (!mayHaveSideEffects(n)) {
        return TernaryValue.TRUE;
      }
      break;
  }

  return TernaryValue.UNKNOWN;
}