OpenEuphoria

Re: C to Eu translator

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Jan 05, 2004
• 406 views

On Sun, 04 Jan 2004 15:46:31 +0100, Juergen Luethje <j.lue at gmx.de>
wrote:

Whilst agreeing with other comments in this thread, and thinking it
would be better to leave it in C, but (learn how to) make it a dll,
there was one point you made I thought deserved special notice:
>How about only translating things that are safe and clear to do,
>e.g. replacing all symbols such as "//", "==", "++", "&&", "||", "~",
I don't believe even these would be safe and clear to translate:
== might want to be '=' in some cases, 'equal()' in others, and not
possible in others (eg a pointer value). You can ++a or a++ in C, so
it would have to be a separate statement in Euphoria, before, after,
or even sometimes in the middle of an expression... && and || may also
sometimes short-circuit differently in C to Euphoria(?).

When I translate C to Euphoria (which is not particularly often), I
start by commenting out the entire source, then using this as a guide
code one function (or line!) at a time, testing thoroughly as I go.

The only example (not specially relevant, either) to hand is a little
mandlebrot demo, first in C:

main(){

int x, y, k;
char *b = " .:,;!/>)|&IH%*#";
float r, i, z, Z, t, c, C;
for (y=30; puts(""), C = y*0.1 - 1.5, y--;){
     for (x=0; c = x*0.04 - 2, z=0, Z=0, x++ < 75;){
        for (r=c, i=C, k=0; t = z*z - Z*Z + r, Z = 2*z*Z + i, z=t,
k<112; k++)
           if (z*z + Z*Z > 10) break;
        printf ("%c", b[k%16]);
        }
     }
 }

...and below in Euphoria:

constant b=" .:,;!/>)|&IH%*#"
atom r, i, c, C, z, Z, t
integer k
    for y=30 to 1 by -1 do
        C=y*0.1-1.5
        puts(1,'\n')
        for x=0 to 74 do
            c=x*0.04-2
            z=0
            Z=0
            r=c
            i=C
            k=0
            while k<112 do
                t=z*z-Z*Z+r
                Z=2*z*Z+i
                z=t
                if z*z+Z*Z>10 then exit end if
                k+=1
            end while
            puts(1,b[remainder(k,16)+1])
        end for
    end for

After some careful study you will see it requires a fairly deep
semantic understanding of the C code in order to rip it apart into
single Euphoria statements, in the right order, were you to try this
automagically. Notice that the inner loop is a while, because k is
used outside it, x and y are no longer declared, the fact that zero
indexing is the norm in C adds to the fun, etc...

HTH,
Pete