float :sqrt ( float $NUMBER )

Returns square root of given number.

# :sqrt example.
:set &NUM i0
:readln &NUM

:set &SQ :sqrt $NUM
:set &PRIME lTRUE

:set &i i2
!while :le $i $SQ
   !if :not :mod $NUM $i
       :set &PRIME lFALSE
   !fi
   :add &i i1
!done

:writeln $NUM s" is " (:fork $PRIME s'' s'not ') s'a prime number.'