How to get bison grammar rule for tokens

Question

Let's say I have the following rules:

rule1 : TOKEN rule2 TOKEN { printf("Found TOKEN\n") ; }

rule2 : ATOKEN { printf("Found ATOKEN\n") ; }

Here, the output will be the following:

Found ATOKEN
Found TOKEN

Because rule2 will be reduced first. Is there any way I can print something as soon as I get TOKEN?

N.B I know I can do that from the scanner when it matches the TOKEN, but I need to print it from bison.

Answer 1

Bison allows actions to be within a rule (known as mid-rule actions).

In your example they could be used like this:

rule1 : TOKEN { printf("Found TOKEN 1\n"); } rule2 TOKEN { printf("Found TOKEN\n") ; }

rule2 : ATOKEN { printf("Found ATOKEN\n") ; }

but you should read the documentation carefully to see if this has the semantic effect that you desire.