C program first follow compiler design

Before proceeding, it is highly recommended to be familiar with the basics in Syntax Analysis, LL 1 parsing, and the rules of calculating First and Follow sets of a grammar. If a Non-Terminal on the R. In case encountered an epsilon i. If reached the end of a production while calculating follow, then the Follow set of that non-terminal will include the Follow set of the Non-Terminal on the L.

This can easily be implemented by recursion. Assumptions :. Skip to content. Change Language. Related Articles. Introduction of Compiler. There are two different C programs to find first and follow of non-terminals in a given grammar. The first of a grammar can be written using structures as well. Here, we have used array data structure to calculate first and follow in C programming.

The first and follow sets are used in compiler designing process. The first set is used in LL parsers which are top — down parsers that read or interpret from left to right.

The follow set is used in LR parsers which are bottom-up parsers that read or interpret from right to left. The LL parsers use leftmost derivations whereas the LR parsers use rightmost derivations.

A predictive parser is constructed using first and follow sets that are associated with Grammar G. If you have any compilation error or doubts in this first and follow of a grammar program in C language, let us know about it in the comment section below.

Bottom-Up and To-Down Parsers uses follow and first functions to make a parsing tree from a given grammar G. This program for follow is not working. It gives segmentation fault. Grammer is not left recursive. Each production of a non terminal is entered on a different line. Only Upper Case letters are Non-Terminals and everything else is a terminal. Calculation of first falls under two broad cases : If the first symbol in the R.

S of the production is a Terminal then it can directly be included in the first set. If the first symbol in the R. S of the production is a Non-Terminal then call the findfirst function again on that Non-Terminal. To handle these cases like Recursion is the best possible solution.

Here again, if the First of the new Non-Terminal contains an epsilon then we have to move to the next symbol of the original production which can again be a Terminal or a Non-Terminal.