If you are really set on feeding raw data into functions,
you can use an image map pigment function, and edit
an image to contain your data in one of the color channels.
#declare TooFun = function {
pigment {
image_map {
tga "fun_map.tga"
}
}
};
#declare TooFunX = function(x) {
TooFun(x,0,0).x
};
