Hi!
> Le 17 févr. 2019 à 14:08, Peng Yu <[email protected]> a écrit :
>
> Hi,
>
> The more I study flex/bison, the more confused I got about when to use
> what actions and what to put in lexer and what to put in grammar.
Usually it's quite clear: build words from letters in the scanner,
build sentences from words in the parser. By "words", I mean
numbers, identifiers, keywords, strings, operators, etc.
> For example, for an assignment,
>
> x=10
>
> it can be processed by the lexer,
>
> [[:alpha:]_][[:alnum:]_]=[[:digit:]+] { /* parse yytext to get the
> name and value, then do the assignment */ }
If you're language is really simple and you can live with that,
then you can. If your language has a rich structure, then it would
be silly.
Note that currently have don't support white spaces (including
\n), you don't support comment (in C, I can write "x /* var */
= /* value */ 42), and then you will have to traverse _again_
your "assignment" to find the lhs and rhs.
Clearly, define what is an identifier in the scanner, then
define their uses in the parser.
> There just seem to be too many possible ways of implementations.
As if often the case in computer science :) But here, there is
a well established and well know best practice.
Cheers!
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