# The role of quotes in Concatenative Combinatory Logic A striking difference between classic Combinatory Logic (CL) and Concatenative Combinatory Logic (CCL) is the use of quotes. The reason we don't need quotes in CL is that we know that Combinators are left associative and reduction moves from left to right meaning that the expression: ``` 𝐒 𝐈 𝐊 ``` is to be understood as: ``` (𝐒 𝐈) 𝐊 ``` We would not even think about applying `𝐈` to `𝐊` as we immediately understand that is `𝐒 𝐈` that must be applied to `𝐊`, not `𝐈` alone. What if we simply view Concatenative combinators as equivalent to classical Combinators but operating in reverse order, right to left, being right associative? If we decided to move right to left and would implicitly consider the right associativity, there would be no need of quotes even if Concatenative combinators could act on anything: there would never be any doubt on what to reduce first. Exactly as it happens in CL. For example, the expression: ``` a b swap zap ``` would be equivalent to: ``` a (b (swap zap)) ``` which makes clear that `swap` can't be reduced before `zap` exactly as in `𝐒 𝐈 𝐊` `𝐈` can't be reduced before `𝐒`. However this would also mean that one could start the evaluation only after having added *all* the combinators to the right (since they are right associative) and this would go against the concatenative principle that says that we can continue the computation at any time by adding more combinators to the right! And here is why, to preserve this essential property, we have to use *quotes* to diffentiate terms that are supposed to be evaluated at a later time (and, hence, are suitable to be used as arguments) by those that are meant to be evaluated immediately.