This repository contains a parser, in the form of an executable file a.out, which addresses the ambiguity caused by dangling else, and is able to parse if-else constructs in C (which may contain dangling else).
The following grammar has been used to tackle the dangling else problem:
stmt → matched | unmatched
matched → if expr then matched else matched | stmt-list | ε
unmatched → if expr then stmt | if expr then matched else unmatched
Run the following commands in the terminal:
$ yacc -d parser.y
$ lex scanner.l
$ gcc lex.yy.c y.tab.c
$ ./a.out
Now, enter a valid and or an invalid input in the terminal, and press enter. Example of such inputs are given below.
if expr then stmt-list
if expr then stmt-list else stmt-list
if expr then if expr then stmt-list else stmt-list
if expr
if expr then else
if expr
if then else
<any input which contains a word which is not 'if', 'then', 'else', 'expr', and 'stmt-list'>