Compute the categories for each node.

prototype/doubt-difftool/main.swift

@@ -41,25 +41,22 @@ func termWithInput(string: String) -> Term? {
 		ts_document_parse(document)
 		let root = ts_document_root_node(document)
 
-		var histogram: [String:Int] = [:]
-
 		struct E: ErrorType {}
-		let result: Term? = try? Cofree
-			.ana { node in
+		return try? Cofree
+			.ana { node, category in
 				let count = ts_node_named_child_count(node)
-				guard let name = String.fromCString(ts_node_name(node, document)) else { throw E() }
-				histogram[name] = (histogram[name] ?? 0) + 1
-				guard count > 0 else { return Syntax.Leaf(name) }
-				return .Indexed((0..<count).map { ts_node_named_child(node, $0) })
-			} (root)
-			.map {
-				let start = ts_node_pos($0).chars
-				return start..<(start + ts_node_size($0).chars)
+				guard count > 0 else { return Syntax.Leaf(category.rawValue) }
+				return try .Indexed((0..<count).map { index in
+					let child = ts_node_named_child(node, index)
+					guard let name = String.fromCString(ts_node_name(child, document)) else { throw E() }
+					guard let category = Category(rawValue: name) else { throw E() }
+					return (child, category)
+				})
+			} (root, Category.Program)
+			.map { node, category in
+				let start = ts_node_pos(node).chars
+				return start..<(start + ts_node_size(node).chars)
 			}
-
-		print(histogram)
-
-		return result
 	}
 }