Myujth

I am implementing the Extended Euclides Algorithm in Maple for arbitrary domains.

In the main loop of the program I have that code:

# Loop
while r_1 <> 0 do;
 print("All is fine before the Quo");
 print(r_0); print(r_1);
 q := ED[Quo](r_0, r_1);
 print("All is fine after the Quo");

 r_aux := r_0 - q * r_1;
 r_0 := r_1; r_1 := r_aux;

 s_aux := s_0 - q * s_1;
 s_0 := s_1; s_1 := s_aux;

 t_aux := t_0 - q * t_1;
 t_0 := t_1; t_1 := t_aux;
od;

Where ED is a Domain object passed as a parameter to the function.

When I call the function with certain arguments, it goes once through the loop and then in the second iteration crashes between the second and third print statement.

Concretely, it produces this output:

 "All is fine before the Quo"
 -87 + 47 _i
 -90 + 43 _i
 "All is fine after the Quo"
 "All is fine before the Quo"
 -90 + 43 _i
 3 + 4 _i
Error, (in E[Domains:-Rem]) cannot determine if this expression is true or false: 0 <= -90*`domains/Gaussian/badge0`(-87, 47)-43*`domains/Gaussian/badge0`(1, 0)*`domains/Gaussian/badge0`(-90, 43)

From this we should infer that calling Gaussian(Z)[Quo] on arguments -90 + 43 _i and 3 + 4 _i should produce this error, right?

Well, think again, because when I try reproducing that from the notebook it decides to stop crashing. Calling:

GI:=Gaussians(Z): a := GI[Input](-90+43*I); b := GI[Input](3+4*I); GI[Quo](a, b);

Produces the output:

 a := -90 + 43 _i
 b := 3 + 4 _i
 -4 + 20 _i

What is going on? Why does it crash inside the function but not in the workbook?