[iter] Make iota() accept invokable for increasing to next item
diff --git a/src/hb-iter.hh b/src/hb-iter.hh
index a0f57ef..f2d81e9 100644
--- a/src/hb-iter.hh
+++ b/src/hb-iter.hh
@@ -656,21 +656,32 @@
template <typename T, typename S>
struct hb_iota_iter_t :
- hb_iter_t<hb_iota_iter_t<T, S>, T>
+ hb_iter_with_fallback_t<hb_iota_iter_t<T, S>, T>
{
hb_iota_iter_t (T start, S step) : v (start), step (step) {}
+ private:
+
+ template <typename S2 = S>
+ auto
+ inc (S s, hb_priority<1>)
+ -> hb_void_t<decltype (hb_invoke (hb_forward<S2> (s), hb_declval<T&> ()))>
+ { v = hb_invoke (hb_forward<S2> (s), v); }
+
+ void
+ inc (S s, hb_priority<0>)
+ { v += s; }
+
+ public:
+
typedef T __item_t__;
static constexpr bool is_random_access_iterator = true;
static constexpr bool is_sorted_iterator = true;
__item_t__ __item__ () const { return hb_ridentity (v); }
- __item_t__ __item_at__ (unsigned j) const { return v + j * step; }
bool __more__ () const { return true; }
unsigned __len__ () const { return UINT_MAX; }
- void __next__ () { v += step; }
- void __forward__ (unsigned n) { v += n * step; }
+ void __next__ () { inc (step, hb_prioritize); }
void __prev__ () { v -= step; }
- void __rewind__ (unsigned n) { v -= n * step; }
hb_iota_iter_t __end__ () const { return *this; }
bool operator != (const hb_iota_iter_t& o) const { return true; }
