repetition of a set of characters

I have the expression

[A-E]|[A-E]{3}|[A-E]{4}

its made to recognize names of angles (A,B,C,D,E) or triangles (ABC,BCD) ect or Rectangles (ABCD,EDCB) ect

BUT

i want to change the expression so that user CANT input an name with the same letter 2 times, names such AAC or ABAE should not be valid names for a trianlge or rectangle.

I ve seen a regex solution of this type of problem here but cant see how i can do this on flex and cant find a way to solve this on the patterns of flex manual. Any help/guide would be helpful.

thanks

---

The easiest way to do this in flex is probably with REJECT :

[A-E]|[A-E]{3}|[A-E]{4}  { for (int i = 0; i < yyleng-1; i++) {
                               if (strchr(yytext+i+1, yytext[i])) {
                                   /* duplicate letter in string */
                                   REJECT; } }
                           return whatever...; }
[A-Z]+                   { return something_else...; }

With this, if you have an input like ABA , it will match the pattern, but due to the duplicate A , it will reject that match and go to match the next-best pattern ( [AZ]+ in this case) and return something_else...

Also note from the flex documentation:

'REJECT' is a particularly expensive feature in terms of scanner performance; if it is used in any of the scanner's actions it will slow down all of the scanner's matching. Furthermore, 'REJECT' cannot be used with the '-Cf' or '-CF' options

---

I have done this

names [A-E]{4}|[A-E]{3}|[A-E]
%%

{names} {int i; for (i = 0; i < yyleng-1; i++) {
                               if (strchr(yytext+i+1, *yytext)) {
                                   /* duplicate letter in string */
                                   REJECT; } }
                           return printf( " %s :VALID NAME n", yytext ); }
[A-Z]+                   { return printf( " %s :INVALID NAMEn", yytext ); }

But it works only for duplicated letters that are at the start of the expression

ex ABA :invalid ABCD:valid ABCA:invalid

BUT

ABBA :valid (it should be invalid) ACBC :valid (it should be invalid)

i must find a way to make i work for every situation

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