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I am very new to lark and am trying to create a simple parser, but I am getting suck on a seemingly simple quesion, why does "No terminal defined for 'i' at line 2 col 1 int "i" 10" show up? Here is my grammar:

start: set_str | set_int COMMENT: ";" /[^\n]/* set_str: "str " STRING " " STRING set_int: "int " STRING " " NUMBER %import common.ESCAPED_STRING -> STRING %import common.SIGNED_NUMBER -> NUMBER %ignore COMMENT %ignore " " %ignore "\n"

and the text input:

int "i" 10 ; this is a comment str "s" "test"

I am new and do not know why this is not working, any tips would be available

also, just a smaller second question is there a way to get rid of the quotes around "i" and "s", because when I remove them they do not become escaped strings anymore.

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  • What is the output you are getting and what is the one you are expecting? Commented Dec 16, 2020 at 5:59
  • I am getting the error and expecting: int - i - 10 str - s "test" Commented Dec 16, 2020 at 6:02
  • How about adding this information to the question? Commented Dec 16, 2020 at 6:16
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    The error messages appears since you only expect a single line, not multiple. you have to change your start rule to repeat what it does, as example with an *. And for your question common defines another terminal CNAME which is probably what you want for names. Commented Dec 16, 2020 at 8:55
  • Ah ok, how would I use *? Commented Dec 16, 2020 at 16:59

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If you read the full error message, you see that the only expected Token is <END-OF-FILE>. This means that there is more input than your grammar consumes. I assume what you want is for start to be parsed as often as possible. This is achieved via an operator in ebnf, with * meaning 'repeat zero or more times' and + meaning 'repeat one or more times'. Therefore to fix your grammar:

start: (set_str | set_int)+ COMMENT: ";" /[^\n]/* set_str: "str" NAME STRING set_int: "int" NAME NUMBER %import common.ESCAPED_STRING -> STRING %import common.CNAME-> NAME %import common.SIGNED_NUMBER -> NUMBER %ignore COMMENT %ignore " " %ignore "\n"

Also note that I made a few other changes: I replaced the first STRING in the set_* with the also from common imported NAME. This is what I assume you want for your second question.

I also removed the " " in the set_*. Since you %ignore them, it isn't required, and it might cause problems in the future.

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