2nd order functions

c/testdata

@@ -146,3 +146,10 @@ def f: (1000,2000); $$f
 [[20,10][1,0] as $x | def f: (100,200) as $y | def g: [$x + $y, .]; . + $x | $$g; $$f[0] | [$$f][0][1] | $$f]
 "woo, testing!"
 [[110.0, 130.0], [210.0, 130.0], [110.0, 230.0], [210.0, 230.0], [120.0, 160.0], [220.0, 160.0], [120.0, 260.0], [220.0, 260.0]]
+
+def f(x): $$x | $$x; $$f([.], . + [42])
+[1,2,3]
+[[[1,2,3]]]
+[[1,2,3],42]
+[[1,2,3,42]]
+[1,2,3,42,42]