(Harder) Yet another use for the const keyword might be to give alternative names for types. Readers may be familiar with languages like Pascal and Modula-2 where code that names types, as exemplified by

is often encouraged, on the basis that it portrays the purpose of the various fields in the Entry record type rather better than the “everything is an integer” approach beloved of C and Java programmers that we have had to adopt in the code in this text. Consider the implications of changing the syntax for ConstDeclarations

The reader might wonder why this simple syntactic change results in it being marked “harder”. The reason is as follows – if this facility is to be of any use, we shall have to extend the production for VarDeclarations as well. At first all that seems necessary is to write

but a little reflection will show that, like this, the grammar is no longer LL (1). Show that it is possible to generate an LL (1) parser by refactorizing the grammar appropriately.