AST Implementation in C | Together C & C++ | Page 1

bitter ospreyBOT Apr 4, 2023, 1:35 PM

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finite sleet Apr 4, 2023, 1:37 PM

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if you want to handle different operators with different precedences, like | and >, you should probably write a proper parser

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I don't see where your build_ast would be doing that, it just goes through tokens from left to right

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and then oddly enough, some precedence is being dealt with in add_child_node, though that's a weird place to do it

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it would be very simple to write a recursive descent parser since the grammar isn't too complicated

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so I'd highly recommend writing a context-free grammar for your shell language first, and then implementing a simple parser for it

subtle shore Apr 4, 2023, 2:39 PM

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finite sleet and then oddly enough, some precedence is being dealt with in `add_child_node`, ...

I was trying to build subtrees and put it all together at the end

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Thank you for your advice, I'll be looking into that

bitter ospreyBOT Apr 4, 2023, 2:44 PM

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@subtle shore Has your question been resolved? If so, run !solved :)

subtle shore Apr 4, 2023, 4:06 PM

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Are these good grammar rules to begin with ?

<command-line> ::= <command> { <pipeline> }
<pipeline>     ::= "|" <command> { <pipeline> }
<command>      ::= { <option> } <word> { <argument> } { <env> } { <heredoc> } { <redirection> }
<option>       ::= "-" <word>
<argument>     ::= <word> | <quoted-word> | <variable>
<word>         ::= <non-space>+
<quoted-word>  ::= '"' <any-chars>* '"'
<variable>     ::= "$" <word>
<env>          ::= <word> "=" <word>
<heredoc>      ::= "<<" <word>
<redirection>  ::= <direction> <word>
<direction>    ::= "<" | ">" | ">>"

finite sleet Apr 4, 2023, 4:14 PM

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looks about right

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though usually the shell doesn't parse arguments, it just passes everything through to the program

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and stuff like matching quoted arguments is more of a lexer job

subtle shore Apr 4, 2023, 4:17 PM

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I see thank you very much, I'll try to build on that

bitter ospreyBOT Apr 5, 2023, 4:50 AM

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subtle shore Jun 2, 2023, 8:23 PM

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!solved

bitter ospreyBOT Jun 2, 2023, 8:23 PM

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#AST Implementation in C