(17BII, 19BII) Easter Sunday solver

[striegel]

This program calculates the date of Easter Sunday for a given year. It is a conversion of the HP Calc solver equation for HP 95LX/100LX/200LX provided by Neil Redmond in his letter to the Palmtop Paper, printed in Volume 7 No 4 July/August 1998. (I would have provided a link to the palmtoppaper.com site itself, but the link there for this particular issue is broken.)

EASTERSUNDAY:EASTR=
0xL(Y:IP(YEAR))+
0xL(G:MOD(G(Y):19)+1)+
0xL(C:IP(G(Y)÷100)+1)+
0xL(X:IP(3xG(C)÷4)-12)+
0xL(Z:IP((8xG(C)+5)÷25)-5)+
0xL(D:IP(5xG(Y)÷4)-G(X)-10)+
0xL(E:MOD(11xG(G)+20+G(Z)-G(X):30))+
0xL(E1:IF(G(E)<0:G(E)+30:G(E)))+
0xL(E2:IF(G(E1)=24:G(E1)+1:IF(G(E1)=25:IF(G(G)>11:G(E1)+1:G(E1)):G(E1))))+
0xL(N:44-G(E2))+
0xL(N1:IF(G(N)<21:G(N)+30:G(N)))+
0xL(N2:7+G(N1)-MOD(G(D)+G(N1):7))+
1xL(N3:IF(G(N2)>31:4+(G(N2)-31)÷100:3+G(N2)÷100)+G(Y)÷1000000)

This is one long and complex solver equation that does not evaluate quickly, so I broke it up to make it easier to check your work as it is entered. Expect it to take 6 or 8 seconds to accept it when input and possibly 20 seconds to verify on a 17BII and longer on a 19BII.

[striegel]

This formula may only be useful for a short time to come, since the churches seem to be agreeing to a fixed date for Easter.

Still, the application of the Let and Get functions is instructive. I learned a lot by studying the technique employed here.

See too that the differences in Solver syntax here between HP LX palmtops and the 17BII and 19BII calculators is minor:

• LX'es use commas instead of colons
• the symbols for multiplication and division are "*" and "/" in the LX instead of "x" and "÷"
  

[brvno]

hello,

it seem HP-17B solver using L a G functions.
This program working on it.