Hello,
I have been going through the very nice "A Complete C++ Example" in the
bison manual and extending it to implement a trivial language. I have a
question about the parsing driver design on this page:
http://www.gnu.org/software/bison/manual/html_node/Calc_002b_002b-Parsing-Driver.html#Calc_002b_002b-Parsing-Driver
I would eventually like to implement a simple command line interface to
my little language. I understand that I can set yyin to some stream that
I control from as-yet-to-be-implemented command line interface. That
interface would also manage command line history etc. I'm struggling to
understand however how bash / python style continuation prompting would
work ( e.g. python sets it's prompt in an interactive session to '...'
when syntax is incomplete ). In order to be able to manage these
prompts, I somehow need to send an indication from bison to flex to my
interface that syntax is incomplete.
The driver provided in the example does not include any parsing state
that I could use as this indication.
I can think of a few approaches to get what I want:
1. use the push-parser design described here
http://www.gnu.org/software/bison/manual/html_node/Push-Decl.html
2. change my YY_DECL to pass parsing state to yylex - the interesting
things that I'd like to pass such as yystack_ are private though ( my
thinking here was that I could examine the stack depth each time yylex
was called ).
3. Dive much deeper into Bison than I intended to and spend some time
learning how to customize behaviour using the C or C++ API.
I have been through the list archives and other Internet resources and
although I can find similar questions posted, I have not been able to
find answers ( or perhaps I do not understand enough yet to parse the
answers. ) Thanks for putting up with my newbiness.
Thanks.
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