I am trying to work through an example in a textbook, but its a few years old and uses maple 2015. I am currently using the 2018 edition of maple. The code is an example of how to generate the points on an elliptic curve given a specific input. 
Here is the example code from the textbook:

epoints := proc(ec, x, ub, p)
    local ecurve, z, pct, k, i;
    pct := 0;
    for k from 0 to p-1 while pct <= ub do
        z := subs(x=k, ec) mod p;
        if z = 0 then
           pct := pct+1;
           ecurve[pct] := [k,z];
        fi:
        if z &^ ((p-1)/2) mod p = 1 then
           z := z &^ ((p+1)/4) mod p;
           ecurve[pct+1] := [k,z];
           ecurve[pct+2] := [k, -z mod p];
           pct := pct+2;
        fi:
    od:
    if pct > ub then
       pct := ub:
    fi:
    seq(ecurve[i], i=1..pct):
end:

Here is my code, written to work with Maple 2018:

ecpoints := proc (ec, x, ub, p) local ecurve, z, pct, k, i;
      pct := 0; for k from 0 to p-1 while pct <= ub
         do z := `mod`(subs(x = k, ec), p);
         if z = 0 then pct := pct+1;
            ecurve[pct] := [k, z] end if;
         if `mod`(z^((1/2)*p-1/2), p) = 1 then
            z := `mod`(z^((1/4)*p+1/4), p) = 1;
           ecurve[pct+1] := [k, z];
           ecurve[pct+2] := [k, `mod`(-z, p)];
           pct := pct+2 end if
   end do;
   if ub < pct then pct := ub end if;

   seq(ecurve[i], i = 1 .. pct)
end proc

The problem is with the output. The output should be [0, 5], [0, 14], [2, 4], [2, 15], [3, 6], [3, 13], [4, 6], [4, 13], [6, 0], [10, 16], [10, 3], [12, 6], [12, 13], [14, 16], [14, 3], [18, 17], [18, 2].
What I get is [0, 5 = 1], [0, 14 = 18], [2, 4 = 1], [2, 15 = 18], [3, 6 = 1], [3, 13 = 18], [4, 6 = 1], [4, 13 = 18], [6, 0], [10, 16 = 1], [10, 3 = 18], [12, 6 = 1], [12, 13 = 18], [14, 16 = 1], [14, 3 = 18], [18, 17 = 1], [18, 2 = 18]. 
Any hints on what I could be doing wrong here or what is going on?

Hello,
I am trying to write a program that will return a partial or complete list of points on an elliptic curve.
In order to do this using examples provided to me, the command "msqrt" was used, which would return FAIL if the conditions were not met.
However, as I am using Maple 2018, this was replcaed with "ModularSquareRoot" which returns an error message.
My question; Is there anyway to circumvent this error message, as it is really causing me a lot of headache. Thanks.