# subtract
> Subtract two complex numbers.
## Usage
```javascript
var csub = require( '@stdlib/math/base/ops/csub' );
```
#### csub( \[out,] re1, im1, re2, im2 )
Subtracts two `complex` numbers where each `complex` number is comprised of a **real** component `re` and an **imaginary** component `im`.
```javascript
var v = csub( 5.0, 3.0, -2.0, 1.0 );
// returns [ 7.0, 2.0 ]
```
By default, the function returns real and imaginary components as a two-element `array`. To avoid unnecessary memory allocation, the function supports providing an output (destination) object.
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var out = new Float64Array( 2 );
var v = csub( out, 5.0, 3.0, -2.0, 1.0 );
// returns [ 7.0, 2.0 ]
var bool = ( v === out );
// returns true
```
## Examples
```javascript
var Complex128 = require( '@stdlib/complex/float64' );
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var real = require( '@stdlib/complex/real' );
var imag = require( '@stdlib/complex/imag' );
var csub = require( '@stdlib/math/base/ops/csub' );
var re;
var im;
var z1;
var z2;
var z3;
var o;
var i;
for ( i = 0; i < 100; i++ ) {
re = round( randu()*100.0 ) - 50.0;
im = round( randu()*100.0 ) - 50.0;
z1 = new Complex128( re, im );
re = round( randu()*100.0 ) - 50.0;
im = round( randu()*100.0 ) - 50.0;
z2 = new Complex128( re, im );
o = csub( real(z1), imag(z1), real(z2), imag(z2) );
z3 = new Complex128( o[ 0 ], o[ 1 ] );
console.log( '(%s) - (%s) = %s', z1.toString(), z2.toString(), z3.toString() );
}
```