Lex And Yacc Program For Infix To Prefix
Lex And Yacc Program For Calculator
In C, strings do not magically expand like they do in other languages. (Or, better said, there really is no string object.) You cannot call strcat(a, b) unless you have already ensured that the char array a has enough space following the NUL terminator to append b. You can't strcat to a string literal, because not only is there not enough space, but also the string literal may be in read-only memory. And you can't strcpy to an unassigned variable and expect sufficient memory to be allocated automatically. (Although $$ is not actually an uninitialised variable, since it is initialised to the value of $1.) So your code is full of buffer overruns, which is undefined behaviour.
Since you can't output operator tokens until after you reduce rules with them (recognize them), you'll need to save the string for the expression before the operator (rather than outputting it as you see it) so it can be emitted after the operator. This means that your rules need to build strings with the translation and only output the string only after parsing a complete expression. There are a number of ways of building strings in C. You can use asprintf or malloc + strcpy/strcat/sprintf, and then worry about when to properly free stuff afterwards. Or you can use some sort of string pool that tracks the memory for you and can deal with cleanup.
Flex is Free scanner alternative to Lex Bison is Free parser generator program. How to recognize “prefix”, “postfix” and “infix”.
- Compiler-construction - lex and yacc program to convert infix to prefix compiler-construction.
- Convert infix to postfix in YACC(Bison). LEX -YACC parser for infix-to-prefix translation. Software Recommendations.