`delete_history'
----------------

delete_history([INDEX])
     :: $B%R%9%H%j$r>C5n$9$k(B.

RETURN
     0

INDEX
     $B>C5n$7$?$$%R%9%H%j$NHV9f(B

   * $B0z?t$,$J$$$H$-(B, $B$3$l$^$G7W;;$7$?%R%9%H%j$rA4$F>C5n$9$k(B.

   * $B0z?t$,$"$k$H$-(B, $B$=$NHV9f$N7k2L$N$_>C5n$9$k(B.

   * $B$3$3$G%R%9%H%j$H$O(B,
     $BHV9f$D$-$N%W%m%s%W%H$KBP$7$F$NF~NO$rI>2A$7$FF@$i$l$?<0(B $B$G(B,
     $B$3$N<0$O(B `@NUMBER' $B$K$h$j<h$j=P$9$3$H$,$G$-$k(B. $B$3$N$3$H$O(B,
     $B%,!<%Y%C%8%3%l%/%7%g%s$N:]$K$b$3$N<0$,@8$-;D$k$3$H$r0UL#$9$k(B.

   * $BBg$-$J<0$,%R%9%H%j$H$7$F;D$C$?>l9g(B,
     $B0J9_$N%a%b%j4IM}$K;Y>c$rMh$9>l9g$,B?$$(B $B$?$a(B, `bsave()'
     $B$J$I$G%U%!%$%k$K%;!<%V$7$F(B, `delete_history()'
     $B$K$h$j%R%9%H%j$r>C5n$7$F$*$/$N$,M-8z$G$"$k(B.

     [0] (x+y+z)^100$
     [1] @0;
     ...
     [2] delete_history(0);
     [3] @0;
     0

