The choice of whether to implement language constructs whose very semantics require that their return value be un-observable is completely arbitrary. Why make y

The choice of whether to implement language constructs whose very semantics require that their return value be un-observable is completely arbitrary. Why make your language more complicated in order to support something that by definition has no effect? Of course things like crippled lambdas can be worked around by using a named function, but the fact that you have to do that in the first place tells you that the person implementing lambdas did so without at the time understanding what they were for. Anyway, it's fine for some kinds of imperative programs, but calling it a functional language is misleading.