interval: the IN operator can now check if an integer value is inlcuded in a range

t_index_test.go

@@ -45,10 +45,11 @@ func TestCollections(t *testing.T) {
 		/*  29 */ {`"abcdef"['x'..]`, nil, `[1:14] interval expression expected integer, got string (x)`},
 		/*  30 */ {`"abcdef"[1+..]`, nil, `[1:12] infix operator "+" requires two non-nil operands, got 1`},
 		/*  31 */ {`"abcdef"[1..4+]`, nil, `[1:15] infix operator "+" requires two non-nil operands, got 1`},
+		/*  32 */ {`r=-1..0..2; "abcdef"[r]`, "fdb", nil},
 	}
 
 	t.Setenv("EXPR_PATH", ".")
 
-	// RunTestSuiteSpec(t, section, inputs, 30)
+	// RunTestSuiteSpec(t, section, inputs, 32)
 	RunTestSuite(t, section, inputs)
 }