Can't parse a certain grammar

[cbeust]

I'm trying to use cakeparse to write the grammar for my shell, https://github.com/cbeust/kash and I can't seem to define a simple grammar to allow either "and" commands:

a && b && c

or "pipe" commands:

a | b | c

Here is what I have, in short:

        val andCommand = singleCommand and zeroOrMore(andAnd and singleCommand)
        val pipeCommand = singleCommand and zeroOrMore(pipe and singleCommand)
        val goal = andCommand or pipeCommand

With that goal, I can only parse one of these two lines but never both.

Am I missing something?

[sargunv]

Sounds like you want to parse something like echo hello && echo world | cat? You'd do something like:

val op = andAnd or pipe
val goal = singleCommand and zeroOrMore(op and singleCommand)

If you want to have the concept of operator precedence, a slightly more complex solution is required. The test module contains a calculator grammar that implements operator precedence (+-*/ operators, also parens): https://github.com/sargunv/cakeparse/blob/master/src/test/kotlin/me/sargunvohra/lib/cakeparse/Calc.kt

Btw, I should warn you that I've only used this library for small toy projects, so it's not very well battle tested. If you do decide to continue to use it anyway, I'd love to hear your feedback and experiences with it.

[sargunv]

On second reading, if you mean parsing something like:

a && b && c
a  | b  | c

but not something like

a && b | c

then the grammar would look like

val andCommand = singleCommand and zeroOrMore(andAnd and singleCommand)
val pipeCommand = singleCommand and zeroOrMore(pipe and singleCommand)
val command = (andCommand or pipeCommand) before terminator
val goal = zeroOrMore(command)