# Category : C Source Code

Archive : CEPHES22.ZIP

Filename : ROUND.C

*

* Round double to nearest or even integer valued double

*

*

*

* SYNOPSIS:

*

* double x, y, round();

*

* y = round(x);

*

*

*

* DESCRIPTION:

*

* Returns the nearest integer to x as a double precision

* floating point result. If x ends in 0.5 exactly, the

* nearest even integer is chosen.

*

*

*

* ACCURACY:

*

* If x is greater than 1/(2*MACHEP), its closest machine

* representation is already an integer, so rounding does

* not change it.

*/

/*

Cephes Math Library Release 2.1: January, 1989

Copyright 1984, 1987, 1989 by Stephen L. Moshier

Direct inquiries to 30 Frost Street, Cambridge, MA 02140

*/

double round(x)

double x;

{

double y, r;

double floor();

/* Largest integer <= x */

y = floor(x);

/* Fractional part */

r = x - y;

/* Round up to nearest. */

if( r > 0.5 )

goto rndup;

/* Round to even */

if( r == 0.5 )

{

r = y - 2.0 * floor( 0.5 * y );

if( r == 1.0 )

{

rndup:

y += 1.0;

}

}

/* Else round down. */

return(y);

}

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