Function apply

src/jit/impl/halide/ast_hl.cpp:377–379

    static void init(FuncRef comp) { comp = cast<hl_comp_type>(0); }
    static void apply(FuncRef comp, Halide::FuncRef in, float) {
        comp += cast<hl_comp_type>(in);
    }
    static void on(FuncRef comp, FuncRef func) { func = cast<hl_out_type>(comp); }
};