Very basic dcg prolog syntax

Question

I am trying to understand prolog and definite clause grammar but I am having a very hard time understanding both of them.

I am really trying to understand how to use

Answer 1

it's not easy to translate do/4 to DCG in meaningful way. I've removed arguments that 'copy' the hidden arguments of the DCG.

do(Sum) -->
    [1],  %check if H is 1
    {  % braces allow 'normal' Prolog code (but we have no access to 'hidden' arguments)
    Additional is H+5,
    Sum is Additional+Additional
    }.

edit sorry I forgot H in Additional is H+5,, should read Additional is 1+5,...