151 lines
3.6 KiB
Markdown
151 lines
3.6 KiB
Markdown
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<!--
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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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# From Binary String
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> Create a [single-precision floating-point number][ieee754] from an [IEEE 754 literal bit representation][@stdlib/number/float32/base/to-binary-string].
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<section class="usage">
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## Usage
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```javascript
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var fromBinaryStringf = require( '@stdlib/number/float32/base/from-binary-string' );
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```
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#### fromBinaryStringf( bstr )
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Creates a [single-precision floating-point number][ieee754] from an [IEEE 754 literal bit representation][@stdlib/number/float32/base/to-binary-string].
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```javascript
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var bstr = '01000000100000000000000000000000';
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var v = fromBinaryStringf( bstr );
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// returns 4.0
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bstr = '01000000010010010000111111011011';
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v = fromBinaryStringf( bstr );
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// returns ~3.14
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bstr = '11111111011011000011101000110011';
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v = fromBinaryStringf( bstr );
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// returns ~-3.14e+38
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```
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The function handles [subnormals][subnormals].
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```javascript
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var bstr = '10000000000000000000000000010110';
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var val = fromBinaryStringf( bstr );
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// returns ~-3.08e-44
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bstr = '00000000000000000000000000000001';
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val = fromBinaryStringf( bstr );
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// returns ~1.40e-45
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```
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The function handles special values.
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```javascript
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var bstr = '00000000000000000000000000000000';
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var val = fromBinaryStringf( bstr );
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// returns 0.0
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bstr = '10000000000000000000000000000000';
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val = fromBinaryStringf( bstr );
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// returns -0.0
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bstr = '01111111110000000000000000000000';
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val = fromBinaryStringf( bstr );
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// returns NaN
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bstr = '01111111100000000000000000000000';
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val = fromBinaryStringf( bstr );
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// returns Infinity
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bstr = '11111111100000000000000000000000';
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val = fromBinaryStringf( bstr );
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// returns -Infinity
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```
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</section>
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<!-- /.usage -->
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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 round = require( '@stdlib/math/base/special/round' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var toFloat32 = require( '@stdlib/number/float64/base/to-float32' );
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var toBinaryStringf = require( '@stdlib/number/float32/base/to-binary-string' );
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var fromBinaryStringf = require( '@stdlib/number/float32/base/from-binary-string' );
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var frac;
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var sign;
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var exp;
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var b;
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var x;
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var y;
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var i;
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// Convert random numbers to IEEE 754 literal bit representations and then convert them back...
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for ( i = 0; i < 100; i++ ) {
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if ( randu() < 0.5 ) {
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sign = -1.0;
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} else {
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sign = 1.0;
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}
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frac = randu() * 10.0;
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exp = round( randu()*100.0 );
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if ( randu() < 0.5 ) {
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exp = -exp;
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}
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x = sign * frac * pow( 2.0, exp );
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x = toFloat32( x );
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b = toBinaryStringf( x );
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y = fromBinaryStringf( b );
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console.log( '%d => %s => %d', x, b, y );
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console.log( x === y );
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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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[subnormals]: https://en.wikipedia.org/wiki/Denormal_number
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[@stdlib/number/float32/base/to-binary-string]: https://www.npmjs.com/package/@stdlib/number/tree/main/float32/base/to-binary-string
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</section>
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<!-- /.links -->
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