Create Email address from names Compiler Design - flex4

Question

Creating email addresses form names
You have given a file containing names of several persons. The file will have exactly one name is each line. You need to create email address ending with #bitmesra.ac.in from those names.
the rule for creating email address is defined below: A name will be expressed in the following form:
............
Let F(s) denote the first character of string s.
so, email id will be F(string 1)F(string 2)........._lastString#bitmesra.ac.in
Some names and their corresponding email id's are listed below as an example
Sachin Ramesh Tendulkar s_r_tendulkar#bitmesra.ac.in
Rahul S Dravid r_s_dravid#bitmesra.ac.in
You need to generate a grammer for this.
note: there may multiple spaces b/w names.
My Code is here
#include<cstdio>
#include<cstring>
#include<cctype>
int main()
{
char str1[100],str2[100];
char str3[] = "#bitmesra.ac.in";
while(gets(str1))
{
int index,k=0;
str2[k] = tolower(str1[0]);
for(int i=1;i<strlen(str1);i++)
{
if(str1[i]==' ')
{
index = i;
if(isalpha(str1[i+1]))
{
k++;
str2[k] = '_';
k++;
str2[k] = tolower(str1[i+1]);
}
}
}
index= index + 2;
for(int i=index;str1[i]!='\0';i++)
{
k++;
str2[k] = tolower(str1[i]);
}
str2[++k] = '\0';
strcat(str2,str3);
printf("%s\n",str2);
}
return 0;
}
How to write CFG Grammar For this.....

Answer 1

What about something like:
optnamelist: /* file can be empty */
| namelist /* do nothing */
namelist: nameseq NL /* process vector */
| namelist NL nameseq /* process vector */
nameseq: name /* create vector and add element 1 */
| nameseq name /* add element to vector */
The lexer should take care of white spaces (eat them). The NL token is a sequence of one or more newlines.
If you add names to the end of a vector, you'll have to process it backward.
Your code implies you're writing this in C. So you could use a fixed sized Vector, e.g.
#define MAX_NAMES 100 /* this will probably be enough :-) */
static int actpos;
static char *myVector[MAX_NAMES];
...
/* "create" vector */
memset(myVector, 0, MAX_NAMES * sizeof(char *));
actpos = 0;
...
/* add name to vector */
myVector[actpos] = strdup($1 /* or $2 */);
if (myVector[actpos) == NULL) ... /* out of memory */
actpos++;
if (actpos >= MAX_NAMES) ... /* name too long */
...
/* process vector */
for (i = actpos - 1; i > 0; --i) {
/* add myVector[i][0] to e-mail address */
free(myVector[i]);
}
/* add myVector[0] to e-mail address */
free(myVector[0]);