LIB "treshold.lib";
version = "$Id: treshold.lib$";
category = "Singularities";
info =
"
LIBRARY: treshold.lib, computes the log canonical treshold
"
proc mod_init()
{
  intvec Numv;   // Numerators
  export(Numv);
  intvec Denv;   // Denominator
  export(Denv);
  int N;         // the length of the intvec
  export(N);
}

proc compute_blowup()
{
// Sets three entries of the  intvecs
  N++;
  Numv[N]=1;
  Denv[N] = 2;

  N++;
  Numv[N]=2;
  Denv[N] = 3;

  N++;
  Numv[N]=4;
  Denv[N] = 6;
}

proc compute_lct()
{
// def d = basering;  // assume we have defined a ring in char 0 outside

  number lct;
  Numv;
  Denv;
  number CKratio = lct;
  for (int i=1;i<=N;i++)
  {
    CKratio = number(Numv[i]+1)/Denv[i];    // this cast with number is required !
    if (CKratio > lct) {lct = CKratio;}
  }
return(lct);
}

>  ring r=0,(x,y),ds;
>   poly f = x2-y3;
>   LIB "treshold.lib";
// ** loaded treshold.lib $Id: treshold.lib$
>   compute_blowup();
>   listvar(Treshold);
// Treshold             [0]  package (S,treshold.lib)
// ::N                  [0]  int 3
// ::Denv               [0]  intvec (3)
// ::Numv               [0]  intvec (3)
// ::compute_lct        [0]  proc from treshold.lib
// ::compute_blowup     [0]  proc from treshold.lib
// ::mod_init           [0]  proc from treshold.lib
>   Treshold::Denv;
2,3,6
>   Treshold::Numv;
1,2,4
>   Treshold::N;
3
>   compute_lct( );   // the treshold of the ordinary cusp
5/6