Problem porting function from C to genexpr code
Hi everyone,
first post here, long time lurker. Recently I've tried to port an open source plugin that models the boss oc-2 octaver in genexpr. The plugin is from the "guitarix" application and is written in FAUST. I've had no problem understanding this language, the "only" problem I 've encountered til now is translating three functions from an header file, written in C (FAUST can actually recall functions written in C). This is the function:
static const float cmos_threshold = 2.5;
static const float cmos_min = -4.0;
static const float cmos_max = 4.0;
float FF_JK_4027(int clock)
{
static bool state;
static float buf;
if((buf < 0) && (clock >= cmos_threshold))
state =! state;
buf = clock;
if(state)
{
return cmos_max;
}
else
{
return cmos_min;
}
}
In particular what is not clear to me is how the first if statement can be computed if "buf" is defined as equal to "clock" after that very statement. From what I understood "static variables" are initialized one time and lasts for all the duration of a program, I thought that "history" could do the trick in giving me access to the memory this way but it's not like that. Translating this in genexpr code is proving quite difficult because genexpr lacks strong typing and such thing as a "static" variable, but I know it can be done. I attach the complete header file, the .dsp file with FAUST code, and my attempt to port the function. Any help from more expert programmers is appreciated.
What is the point of translating the Faust generated source to genexpr in the first place ?
Hi sletz! If you're referring to the fact that I could just take the FAUST generated code and wrap it in a max external instead of porting in gen~ the answer is that I've never done it before, and I currently don't have FAUST 2 installed on my computer, which, as far as I know, is necessary to generate C code. Also from what I've read on the FAUST repository FAUST2 it's quite tricky to install, and I have 0 experiences with compiling, libraries and all that kind of stuff. If you're referring to use the faustgen~ external the fact is it won't function with this specific code because it recalls foreign functions from the header file I posted above, and I remember you saying in another topic that faustgen~ doesn't have access to foreign functions for compiling issues. Maybe this feature has been added recently? Also I'm taking all this as an exercise to improve my coding ability in genexpr.
I believe the equivalent genexpr is the following. This compiles and appears to have approximately the correct logic.
ffjk4027(clock) {
History state;
History buf;
if (buf < 0 && clock >= 2.5) {
state = !state;
}
buf = clock;
if (state) {
return 4;
} else {
return -4;
}
}(One caveat however is that the use of static variables in functions like the above code is that this variable will be shared between *all* calls of the function, which is not the case in Gen. Every lexical instance of the call to ffjk4027() in gen will create a new state/buf to go with it. If this isn't what you need, pass the History objects in as arguments to a function instead. But I'm guessing that the postfix "4027" means that this code was generated for single call, which means you don't have to worry.)
Thank you very much Graham! I've compiled the original C functions and it seems equivalent: no matter the input it always gives me -4. Also I had implemented a system based on the use of a "data" but I think is the same with history, so I'll use this one.