/
Tolerance.scala
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/
Tolerance.scala
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/*
* Copyright 2001-2013 Artima, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.scalactic
import TripleEqualsSupport.Spread
/**
* Trait containing an implicit conversion that adds a <code>+-</code> method to <code>Numeric</code> types, which enables
* spreads to be expressed in terms of a <em>pivot</em> and <em>tolerance</em>.
*
* <p>
* For example, the <code>TripleEquals</code> trait (and its type-checking siblings <code>TypeCheckedTripleEquals</code> and
* <code>ConversionCheckedTripleEquals</code>) enable you to write:
* </p>
*
* <pre class="stHighlighted">
* a === (<span class="stLiteral">1.0</span> +- <span class="stLiteral">0.1</span>)
* </pre>
*
* @author Bill Venners
*/
trait Tolerance {
/**
* Wrapper class with a <code>+-</code> method that, given a <code>Numeric</code> argument, returns a <code>Spread</code>.
*
* @param tolerance the tolerance with which to create (and return) a <code>Spread</code>
*
* @author Bill Venners
*/
final class PlusOrMinusWrapper[T: Numeric](pivot: T) {
/**
* Creates and returns a <code>Spread<code> from the <code>pivot</code> passed to the constructor and
* the <code>tolerance</code> passed to this method.
*
* @param tolerance the tolerance with which to create (and return) the <code>Spread</code>
*/
def +-(tolerance: T): Spread[T] = {
val numeric = implicitly[Numeric[T]]
if (numeric.lteq(tolerance, numeric.zero))
throw new IllegalArgumentException(tolerance.toString + " passed to +- was zero or negative. Must be a positive non-zero number.")
// throw newTestFailedException(Resources("negativeOrZeroRange", tolerance.toString))
Spread(pivot, tolerance)
}
}
import scala.language.implicitConversions
/**
* Implicitly converts an object of a <code>Numeric</code> type to a <code>PlusOrMinusWrapper</code>,
* to enable a <code>+-</code> method to be invoked on that object.
*/
implicit def convertNumericToPlusOrMinusWrapper[T : Numeric](pivot: T): PlusOrMinusWrapper[T] = new PlusOrMinusWrapper(pivot)
}
/**
* Companion object to trait <code>Tolerance</code> that facilitates the importing of <code>Tolerance</code> members as
* an alternative to mixing it in. One use case is to import <code>Tolerance</code> members so you can use
* them in the Scala interpreter:
*
* <pre class="stREPL">
* $ scala -classpath scalactic.jar
* Welcome to Scala version 2.10.0
* Type in expressions to have them evaluated.
* Type :help for more information.
*
* scala> import org.scalactic._
* import org.scalactic._
*
* scala> import Tolerance._
* import Tolerance._
*
* scala> 1.0 +- 0.1
* res0: org.scalactic.TripleEqualsSupport.Spread[Double] = Spread(1.0,0.1)
* </pre>
*/
object Tolerance extends Tolerance