# Set High Word
> Set the more significant 32 bits of a [double-precision floating-point number][ieee754].
## Usage
```javascript
var setHighWord = require( '@stdlib/number/float64/base/set-high-word' );
```
#### setHighWord( x, high )
Sets the more significant 32 bits (higher order word) of a [double-precision floating-point number][ieee754] `x` to a bit sequence represented by an unsigned 32-bit integer `high`. The returned `double` will have the same less significant 32 bits (lower order word) as `x`.
```javascript
var high = 5 >>> 0; // => 0 00000000000 00000000000000000101
var y = setHighWord( 3.14e201, high ); // => 0 00000000000 0000000000000000010110010011110010110101100010000010
// returns 1.18350528745e-313
var PINF = require( '@stdlib/constants/float64/pinf' ); // => 0 11111111111 00000000000000000000 00000000000000000000000000000000
high = 1072693248 >>> 0; // => 0 01111111111 00000000000000000000
// Set the higher order bits of `+infinity` to return `1`:
y = setHighWord( PINF, high ); // => 0 01111111111 0000000000000000000000000000000000000000000000000000
// returns 1.0
```
## Examples
```javascript
var pow = require( '@stdlib/math/base/special/pow' );
var round = require( '@stdlib/math/base/special/round' );
var randu = require( '@stdlib/random/base/randu' );
var MAX_UINT32 = require( '@stdlib/constants/uint32/max' );
var setHighWord = require( '@stdlib/number/float64/base/set-high-word' );
var high;
var frac;
var exp;
var x;
var y;
var i;
// Generate a random double-precision floating-point number:
frac = randu() * 10.0;
exp = -round( randu() * 323.0 );
x = frac * pow( 10.0, exp );
// Replace the higher order word of `x` to generate new random numbers having the same lower order word...
for ( i = 0; i < 100; i++ ) {
high = round( randu()*MAX_UINT32 );
y = setHighWord( x, high );
console.log( 'x: %d. new high word: %d. y: %d.', x, high, y );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/number/float64/base/set_high_word.h"
```
#### stdlib_base_float64_set_high_word( high, \*x )
Sets the more significant 32 bits of a double-precision floating-point number.
```c
#include
uint32_t high = 1074339512;
double x = 0.0;
stdlib_base_float64_set_high_word( high, &x );
```
The function accepts the following arguments:
- **high**: `[in] uint32_t` higher order word.
- **x**: `[in-out] double*` reference to (and destination for) a double-precision floating-point number.
```c
void stdlib_base_float64_set_high_word( const uint32_t high, double *x );
```
### Examples
```c
#include "stdlib/number/float64/base/set_high_word.h"
#include
#include
int main( void ) {
uint32_t high[] = { 1074339512, 1074339513, 1074339514, 1074339515 };
double x = 3.14;
int i;
for ( i = 0; i < 4; i++ ) {
stdlib_base_float64_set_high_word( high[ i ], &x );
printf( "high: %u => %lf\n", high[ i ], x );
}
}
```
[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
[@stdlib/number/float64/base/get-high-word]: https://github.com/stdlib-js/number/tree/main/float64/base/get-high-word
[@stdlib/number/float64/base/set-low-word]: https://github.com/stdlib-js/number/tree/main/float64/base/set-low-word