Some new GP features
halfgcd for integers
Let a, b be two integers. halfgcd(a,b) returns [M, [x, y] ]
where M is a 2 × 2 matrix of determinant ±1 such that
M*[x,y] = [a,b] and a ≥
p
max(|x|, |y|) > b
? [M,C] = halfgcd(23,59)
%14 = [[3,-1;-5,2],[10,3]~]
? M*[23,59]~
%15 = [10,3]~