ceil/floor/truncate/round return integers.

sdk/lib/core/double.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.core;
 
 // TODO: Convert this abstract class into a concrete class double
 // that uses the patch class functionality to account for the
 // different platform implementations.
 
@@ skipping 27 matching lines @@
   /** Euclidean modulo operator. */
   double operator %(num other);
 
   /** Division operator. */
   double operator /(num other);
 
   /**
    * Truncating division operator.
    *
    * The result of the truncating division [:a ~/ b:] is equivalent to
-   * [:(a / b).truncate().toInt():].
+   * [:(a / b).truncate():].
    */
   int operator ~/(num other);
 
   /** Negate operator. */
   double operator -();
 
   /** Returns the absolute value of this [double]. */
   double abs();
 
   /**
-   * Returns the integer value closest to this [double].
+   * Returns the integer closest to `this`.
+   *
+   * Rounds away from zero when there is no closest integer:
+   *  [:(3.5).round() == 4:] and [:(-3.5).round() == -4:].
+   *
+   * If `this` is not finite (`NaN` or infinity), throws an [UnsupportedError].
+   */
+  int round();
+
+  /**
+   * Returns the greatest integer no greater than `this`.
+   *
+   * If `this` is not finite (`NaN` or infinity), throws an [UnsupportedError].
+   */
+  int floor();
+
+  /**
+   * Returns the least integer no smaller than `this`.
+   *
+   * If `this` is not finite (`NaN` or infinity), throws an [UnsupportedError].
+   */
+  int ceil();
+
+  /**
+   * Returns the integer obtained by discarding any fractional
+   * digits from `this`.
+   *
+   * If `this` is not finite (`NaN` or infinity), throws an [UnsupportedError].
+   */
+  int truncate();
+
+  /**
+   * Returns the integer value, as a double, closest to `this`.
    *
    * Rounds away from zero when there is no closest integer:
    *  [:(3.5).round() == 4:] and [:(-3.5).round() == -4:].
    */
-  double round();
-
-  /** Returns the greatest integer value no greater than this [double]. */
-  double floor();
-
-  /** Returns the least integer value that is no smaller than this [double]. */
-  double ceil();
+  double roundToDouble();
 
   /**
-   * Returns the integer value obtained by discarding any fractional
-   * digits from this [double].
+   * Returns the greatest integer value no greater than `this`.
+   *
+   * The result is a double.
    */
-  double truncate();
+  double floorToDouble();
+
+  /**
+   * Returns the least integer value no smaller than `this`.
+   *
+   * The result is a double.
+   */
+  double ceilToDouble();
+
+  /**
+   * Returns the integer obtained by discarding any fractional
+   * digits from `this`.
+   *
+   * The result is a double.
+   */
+  double truncateToDouble();
 
   /**
    * Provide a representation of this [double] value.
    *
    * The representation is a number literal such that the closest double value
    * to the representation's mathematical value is this [double].
    *
    * Returns "NaN" for the Not-a-Number value.
    * Returns "Infinity" and "-Infinity" for positive and negative Infinity.
    * Returns "-0.0" for negative zero.
@@ skipping 13 matching lines @@
    * returns the corresponding double value.
    *
    * If the [soure] is not a valid double literal, the [handleError]
    * is called with the [source] as argument, and its return value is
    * used instead. If no handleError is provided, a [FormatException]
    * is thrown.
    */
   external static double parse(String source,
                                [double handleError(String source)]);
 }