!  TryNumber is the only routine which really does any character-level
!  parsing, since that's normally left to the Z-machine.
!  It takes word number "wordnum" and tries to parse it as an (unsigned)
!  decimal number, returning
!
!  -1000                if it is not a number
!  the number           if it has between 1 and 4 digits
!  10000                if it has 5 or more digits.
!
!  (The danger of allowing 5 digits is that Z-machine integers are only
!  16 bits long, and anyway this isn't meant to be perfect.)
!
!  Using NumberWord, it also catches "one" up to "twenty".
!
!  Note that a game can provide a ParseNumber routine which takes priority,
!  to enable parsing of odder numbers ("x45y12", say).
! ----------------------------------------------------------------------------

[ TryNumber wordnum   i j c num len mul tot d digit;

   i=wn; wn=wordnum; j=NextWord(); wn=i;
   j=NumberWord(j); if (j>=1) return j;

   i=wordnum*4+1; j=parse->i; num=j+buffer; len=parse->(i-1);

   tot=ParseNumber(num, len);  if (tot~=0) return tot;

   if (len>=4) mul=1000;
   if (len==3) mul=100;
   if (len==2) mul=10;
   if (len==1) mul=1;

   tot=0; c=0; len=len-1;

   for (c=0:c<=len:c++)
   {   digit=num->c;
       if (digit=='0') { d=0; jump digok; }
       if (digit=='1') { d=1; jump digok; }
       if (digit=='2') { d=2; jump digok; }
       if (digit=='3') { d=3; jump digok; }
       if (digit=='4') { d=4; jump digok; }
       if (digit=='5') { d=5; jump digok; }
       if (digit=='6') { d=6; jump digok; }
       if (digit=='7') { d=7; jump digok; }
       if (digit=='8') { d=8; jump digok; }
       if (digit=='9') { d=9; jump digok; }
       return -1000;
     .digok;
       tot=tot+mul*d; mul=mul/10;
   }
   if (len>3) tot=10000;
   return tot;
];