(42, all flavours) Integer Division - how?

[Albert Chan]

(12-13-2020 01:18 PM)Albert Chan Wrote:  We had assumed q never overflow, which results in |r| ≤ 1

Assuming q is correctly rounded (mode round-to-nearest), r = 0 or -1

The code is simplified to correct, or not correct.

PHP Code:

function idiv3(a,b)         -- assumed b > 0
    local q, c = floor(a/b), b+1
    a, b = a%b - a%c, q%c   -- a-b = [2-2c, c-2]
    if a==b or a==b-c then return q end    
    return q-1
end