6.13.2 `dabs', `dexp', `dlog', `dsqrt'
--------------------------------------

dabs(NUM)
     :: $B@dBPCM(B |NUM| $B$r5a$a$k(B.

dexp(NUM)
     :: $BH!?tCM(B exp(NUM) $B$r5a$a$k(B.

dlog(NUM)
     :: $BBP?tCM(B log(NUM) $B$r5a$a$k(B.

dsqrt(NUM)
     :: $BJ?9T:,(B sqrt(NUM) $B$r5a$a$k(B.

RETURN
     $BG\@:EYIbF0>.?t(B

NUM
     $B?t(B

   * $B=iEyH!?t$r?tCME*$K7W;;$9$k(B.

   * $B$3$l$i$NH!?t$O(B C $B8@8l$NI8=`?t3X%i%$%V%i%j$rMQ$$$k(B.  $B$7$?$,$C$F(B,
     $B7W;;7k2L$O%*%Z%l!<%F%#%s%0%7%9%F%`$H%3%s%Q%$%i$K0MB8$9$k(B.

   * `dabs()'$B$H(B`dsqrt()'$B$r=|$-!"(B
     $BJ#AG?t$KBP$7$F$O@5$7$/$J$$7k2L$rJV$9$N$GCm0U$7$J$1$l$P$J$i$J$$(B.

   * @pi $B$J$I$N%7%s%\%k$r0z?t$KM?$($k$3$H$O$G$-$J$$(B.

     [0] dexp(1);
     2.71828

