OpenEuphoria

Re: The "evolution" of GA Math

• Posted by DB James <larch at adelphia.net> Oct 03, 2005
• 608 views

Al Getz wrote:
SNIP
> 
> Hi Quark,
> 
> Yes, i had found that eval.e cant handle a multiplication before
> a function such as a*ln(x) or k*sin(x), etc., so i ended up doing
> the same thing temporarily.  Putting parens around the function
> seemed to work so i did that too: y=a*(ln(x+1))
> This means i was doing basically the same thing you were doing :)
> BTW i used "ln" instead of "log" because in the math world "log"
> usually refers to log base 10 and ln refers to log base e, and
> in GA Math i ended up making it skip the "l" and the "n" as variables
> (it wanted to make l and n variables at first).
> 
> The interesting thing is, both of your runs came out algebraically
> either exact or nearly so, so perhaps my run was a fluke or something
> where it somehow got sidetracked, or perhaps returning a large
> negative number as a 'penalty' isnt a good idea?
> So what did you use for the log function in GA Math then...
> when the number is positive i guess it's log(), but what about
> when it's negative, or zero?  Those are three possibilities so
> if i knew what lines you used in GA Math for function #11 i could
> try the same.
> 
> 
> Take care,
> Al

Hello Al,

Here is the relevant code:

            elsif op=11 then
                --decimal fraction
                if p[i][REG][from1]>0 then
                    p[i][REG][store]=log(p[i][REG][from1])
                else
                    --"null" response...
                    p[i][REG][store]=0
                end if

The GA Math "experience" seems to be a study in the complex interaction of
decisions made in coding.  There never seems to be a state where one can say: "I
have ideally optimized this".  If we had access to a nice used NSA
super-computer, we could set it to work on ways to evolve self-optimizing code
:^D

By the way, you may want to pop the already existing trig functions of eval.e 
into GA Math to see what effect that has on some of your test problems.  I dont't
know how you want to handle the modification necessary to get GA Math to deal
with multiple-character tokens in formula entry.  Here is what I did, in case it
is useful to you:

At the top I added a new constant to be a list of recognizable functions:
constant EVALKEYWORDS={"log"}--many could be added here

Then I created the MarkMatch function (not tested carefully yet):
-------------------------------------------------
function MarkMatch(sequence s,sequence m)
    --Quark 10/05 --create sequence with match locs of m in s where m is a
    --sequence like {"this","that","whatever"} and s is a string
    integer x,oldx
    sequence t
    t={}
    for i=1 to length(m) do
        x=match(m[i],s)
        while x do
            for j=1 to length(m[i]) do
                t&=x+j-1
            end for
            oldx=x
            if x+length(m[i])<=length(s) then
                x=match(m[i],{s[x+length(m[i])]})
                if x then
                    x+=oldx+length(m[i])-1  
                end if
            end if
        end while
    end for
    return t -- or sort(t)
end function
-------------------------------------------------

Then used that in GetFormula() this way:
skip=MarkMatch(f,EVALKEYWORDS)--e.g. if f="a=log(x)", skip={3,4,5}
    indicating "log"
    cnt=2
    t={}
    for i=x+1 to length(f) do
        if not find(i,skip) then--<<<< * This is the key line *
            if Alpha(f[i]) then
                if not find(f[i],t) then
                    t&=f[i]
                    cnt+=1
                end if
            end if
        end if
    end for
    return {f,t}
-------------------------------------------------------

You may well have a handier way to deal with all that.

Your investigations have been really interesting -- please continue to let me
know how it goes...

--Quark