a prime year

[Paul Dale]

(01-02-2017 02:17 PM)Harald Wrote:  I'll vote for a "lastprime" function in the WP34s if you are going to ask more questions like that

The code is in XROM, just not included in any image:

Code:

        XLBL"PREVPRIME"
            INTM?
                JMP prevprime_xin
            DBL?
                JMP prevprime_dbl
            xIN MONADIC

            _INT 50
            _INT 16
            10[^x]
            STO+ Y
            RCL Z
            x>? Z
                ERR ERR_DOMAIN
            MIN
            JMP prevprime_skip_xin

prevprime_dbl::        [infinity]?
                ERR ERR_DOMAIN
prevprime_xin::        xIN MONADIC
prevprime_skip_xin::    CEIL
            PRIME?
                DEC X
            x[<=]1?
                ERR ERR_DOMAIN
            EVEN?
prevprime_loop::        DEC X
            x[<=]1?
                JMP prime_2
            PRIME?
                xOUT xOUT_NORMAL
            DEC X
            JMP prevprime_loop

It would be easy enough to key this in as a user program.


Pauli