use new iterator protocol

src/baseutils.jl

@@ -26,11 +26,18 @@ best_arg, best_val = argmax(f, iter)
 Computes the first element of iterator, on which f takes its maximum.
 """
 function argmax(f, iter)
-    state = start(iter)
-    best_arg, state = next(iter, state)
+    iter_result = iterate(iter)
+    if iter_result === nothing
+        throw(ArgumentError("Cannot compute the argmax of an empty collection"))
+    end
+    best_arg, state = iter_result
     best_val = f(best_arg)
-    while !done(iter,state)
-        arg, state = next(iter,state)
+    while true
+        iter_result = iterate(iter, state)
+        if iter_result === nothing
+            break
+        end
+        arg, state = iter_result
         val = f(arg)
         if val > best_val
             best_val = val
@@ -40,7 +47,6 @@ function argmax(f, iter)
     best_arg, best_val
 end
 
-
 w_component(::Type{Point{N, T}}) where {N, T} = T(1)
 w_component(::Type{Vec{N, T}}) where {N, T} = T(0)