Press n or j to go to the next uncovered block, b, p or k for the previous block.
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* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* 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.
*/
'use strict';
// MODULES //
var Uint32Array = require( '@stdlib/array/uint32' );
var Float64Array = require( '@stdlib/array/float64' );
var HIGH = require( './high.js' );
// VARIABLES //
var FLOAT64_VIEW = new Float64Array( 1 );
var UINT32_VIEW = new Uint32Array( FLOAT64_VIEW.buffer );
// MAIN //
/**
* Sets the more significant 32 bits of a double-precision floating-point number.
*
* ## Notes
*
* ```text
* float64 (64 bits)
* f := fraction (significand/mantissa) (52 bits)
* e := exponent (11 bits)
* s := sign bit (1 bit)
*
* |-------- -------- -------- -------- -------- -------- -------- --------|
* | Float64 |
* |-------- -------- -------- -------- -------- -------- -------- --------|
* | Uint32 | Uint32 |
* |-------- -------- -------- -------- -------- -------- -------- --------|
* ```
*
* If little endian (more significant bits last):
*
* ```text
* <-- lower higher -->
* | f7 f6 f5 f4 f3 f2 e2 | f1 |s| e1 |
* ```
*
* If big endian (more significant bits first):
*
* ```text
* <-- higher lower -->
* |s| e1 e2 | f1 f2 f3 f4 f5 f6 f7 |
* ```
*
* In which Uint32 can we find the higher order bits? If little endian, the second; if big endian, the first.
*
* ## References
*
* - [Open Group][1]
*
* [1]: http://pubs.opengroup.org/onlinepubs/9629399/chap14.htm
*
* @param {number} x - double
* @param {uinteger32} high - unsigned 32-bit integer to replace the higher order word of `x`
* @returns {number} double having the same lower order word as `x`
*
* @example
* var high = 5 >>> 0; // => 0 00000000000 00000000000000000101
*
* var y = setHighWord( 3.14e201, high ); // => 0 00000000000 0000000000000000010110010011110010110101100010000010
* // returns 1.18350528745e-313
*
* @example
* var PINF = require( '@stdlib/constants/float64/pinf' ); // => 0 11111111111 00000000000000000000 00000000000000000000000000000000
*
* var high = 1072693248 >>> 0; // => 0 01111111111 00000000000000000000
*
* // Set the higher order bits of `+infinity` to return `1`:
* var y = setHighWord( PINF, high ); // => 0 01111111111 0000000000000000000000000000000000000000000000000000
* // returns 1.0
*/
function setHighWord( x, high ) {
FLOAT64_VIEW[ 0 ] = x;
UINT32_VIEW[ HIGH ] = ( high >>> 0 ); // identity bit shift to ensure integer
return FLOAT64_VIEW[ 0 ];
}
// EXPORTS //
module.exports = setHighWord;
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