binarysearch(v, x) = {
    local(
        minm = 1,
        maxm = length(v),
        guess = floor(maxm/2+minm/2)
    );

    while(v[guess] != x,
        if(v[guess] < x, minm = guess + 1, maxm = guess - 1);
        if(minm > maxm,
            guess = 0;
            break
        );
        guess = floor(maxm/2+minm/2)
    );

    return(guess);
}

idx = binarysearch([1,4,9,16,25,36,49,64,81,100,121,144], 121);
if(idx, \
    print("Item exists on index ", idx), \
    print("Item does not exist anywhere.") \
)