106 lines
2.4 KiB
Markdown
106 lines
2.4 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Flipsign
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> Return a [double-precision floating-point number][ieee754] with the magnitude of `x` and the sign of `x*y`.
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<section class="usage">
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## Usage
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```javascript
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var flipsign = require( '@stdlib/math/base/special/flipsign' );
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```
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#### flipsign( x, y )
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Returns a [double-precision floating-point number][ieee754] with the magnitude of `x` and the sign of `x*y`; i.e., only return `-x` when `y` is a negative number.
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```javascript
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var z = flipsign( -3.14, 10.0 );
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// returns -3.14
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z = flipsign( -3.14, -1.0 );
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// returns 3.14
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z = flipsign( 1.0, -0.0 );
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// returns -1.0
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z = flipsign( -3.14, -0.0 );
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// returns 3.14
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z = flipsign( -0.0, 1.0 );
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// returns -0.0
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z = flipsign( 0.0, -1.0 );
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// returns -0.0
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- According to the [IEEE 754][ieee754] standard, a `NaN` has a biased exponent equal to `2047`, a significand greater than `0`, and a sign bit equal to **either** `1` **or** `0`. In which case, `NaN` may not correspond to just one but many binary representations. Accordingly, care should be taken to ensure that `y` is **not** `NaN`, else behavior may be indeterminate.
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var randu = require( '@stdlib/random/base/randu' );
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var flipsign = require( '@stdlib/math/base/special/flipsign' );
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var x;
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var y;
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var z;
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var i;
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// Generate random double-precision floating-point numbers `x` and `y` and flip the sign of `x` only if `y` is negative...
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for ( i = 0; i < 100; i++ ) {
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x = (randu()*100.0) - 50.0;
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y = (randu()*10.0) - 5.0;
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z = flipsign( x, y );
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console.log( 'x: %d, y: %d => %d', x, y, z );
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
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</section>
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<!-- /.links -->
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