(42, all flavours) Integer Division - how?

[Werner]

(12-17-2020 06:41 PM)Albert Chan Wrote:  Your half-way-case had a typo. It should be b := Qq % c

Thanks, I corrected it.

Quote:If Cc00/Xx fractional part is 0.5, it implied Cc000 / Xx is integer, ends in 5.

No.. each 0 is the length of a half integer, so for a 12 digit machine it is 000000 and for Free42/DM42 it's 17 zeroes ;-)

Cc00 = Qq*Xx + Rr is the first part of dividing a multiprecision number stored in sequential registers by a number not exceeding a single register:

R1 R2 R3 R4 R5
Aa Bb Cc Dd Ee ... / Xx

At each step you have the carry from the previous step, Cc, and so you have to do
CcYY = Qq*Xx + Rr

with Rr next step's Cc.

We can only work with 2 letters at the same time, so first

Cc00 = Qq*Xx + Rr (as previously covered)
t := Yy-Xx+Rr; (because Yy+Rr may overflow)
Cc := MOD(t,Xx);
IF t>0 then
Qq := Qq + (t-Cc)/Xx + 1;
end;
Yy := Qq;

Werner