diff options
Diffstat (limited to 'src/cmd/map/sqrt.c')
-rw-r--r-- | src/cmd/map/sqrt.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/src/cmd/map/sqrt.c b/src/cmd/map/sqrt.c new file mode 100644 index 00000000..1f933384 --- /dev/null +++ b/src/cmd/map/sqrt.c @@ -0,0 +1,52 @@ +/* + sqrt returns the square root of its floating + point argument. Newton's method. + + calls frexp +*/ + +#include <u.h> +#include <libc.h> + +double +sqrt(double arg) +{ + double x, temp; + int exp, i; + + if(arg <= 0) { + if(arg < 0) + return 0.; + return 0; + } + x = frexp(arg, &exp); + while(x < 0.5) { + x *= 2; + exp--; + } + /* + * NOTE + * this wont work on 1's comp + */ + if(exp & 1) { + x *= 2; + exp--; + } + temp = 0.5 * (1.0+x); + + while(exp > 60) { + temp *= (1L<<30); + exp -= 60; + } + while(exp < -60) { + temp /= (1L<<30); + exp += 60; + } + if(exp >= 0) + temp *= 1L << (exp/2); + else + temp /= 1L << (-exp/2); + for(i=0; i<=4; i++) + temp = 0.5*(temp + arg/temp); + return temp; +} |