Algorithms for moving the cursor to a date on a 12 month rotating calendar in Emacs

Question

GOAL:  The goal of this thread is to create two (2) mathematical formulas to replace the long-hand solution by @lawlist in the function lawlist-calend

Answer 1

I must be missing something because it looks like the formulas are as simple as (pseudocode):

first  = 9 * ( rows - 1 ) 
second = 6 + 25 * ( cols - 1 )

based on your edit, you can calculate the rows and cols to move with:

if target > display
   difference = target - display
else 
   difference = 12 + target - display
 rows = difference / 3 
 cols = difference % 3
 rowmove = 9 * rows 
 colmove = 6 + 25 * cols

And then use the formula above.

My attempt at elisp:

(let difference (if (>= target-month display-month) 
                      (- target-month display-month) 
                    (- (+ target-month 12) display-month)))
(let rows (/ difference 3))
(let cols (% difference 3))
(let rowmove (* 9 rows))   
(let colmove (+ 6 (* 25 cols)))