I whether or not there is a stack is similar to the complementary nature of foldL vs parallel fold (ie Clojure's core/reduce vs reducers). Left-to-right concate

I whether or not there is a stack is similar to the complementary nature of foldL vs parallel fold (ie Clojure's core/reduce vs reducers). Left-to-right concatenative languages make use of a stack and are appropriate for side effects and stream processing. However, there are pure concatenative languages that operate in parallel via term rewriting, which has a computational model akin to that of a DNA computer.