There is a way to make the D code faster: prepending a cell in
left() is a slow operation:
void right() pure nothrow {
this.position++;
if (this.position == this.tape.length)
this.tape ~= this.blank;
}
void left() pure nothrow {
if (this.position == 0)
this.tape = this.blank ~ this.tape;
else
this.position--;
}
If you want to make the code faster (useful for a larger Busy
Beaver simulation), you keep two tapes as two dynamic arrays. One
tape represents the items on the right of the origin and the
other tape on the left of the origin. So the position becomes a
signed integer and both left() and right() use a fast append
operation.
Bye,
bearophile
