EBNF: expr
digit = '1' | '2' | '3' | '4'
number = digit digit*
expr = number (('+' | '-') number)*
;EBNF
I was able to evaluate this expression immediately in the Listener and on a
word I defined in my own vocab.
Doing the immediate eval leaves
T{ parser f ~action-parser~ f 4820 }
How am I expected to use this notation?. I read: "a parser instance",
constant f (false), "something to do with a parse and its action", another
false constant, number 4820. I can't do any real thinking with that. Why
don't we have more informative print-strings for our Tuples/Objects?
Then:
"123+456" expr
Will result in a parse tree left on the stack.
This leaves
V{ ~vector~ ~vector~ }
Again there is the opacity problem. What does the "~vector~" mean? And why
would I ever want to read such a general description of a 2-vector? It
doesn't say much about what is in the tree.
How are the rule statements parsed? There are no periods between them. The
EBNF parser must scan forward for the next "<nonterminal>=", to know where
the previous rule ends. Is this what is happening?
The EBNF: name ...
;EBNF expression results in a word with 'name' defined that
parses the
given grammar.
You can also do:
<EBNF
digit = '1' | '2' | '3' | '4'
number = digit digit*
expr = number (('+' | '-') number)*
EBNF>
This leaves a parser object on the stack which you can call
'parse' on:
"123" over parse .
This one failed at the listener:
"Generic word parse does not define a method for the parser class.
Dispatching on object:..."
Or:
"123" [EBNF
digit = '1' | '2' | '3' | '4'
number = digit digit*
expr = number (('+' | '-') number)*
EBNF] .
produces
V{ V{ "1" V{ "2" "3" } } V{ } }
which I suppose is the parse tree for the last rule expr.
The [EBNF ... EBNF] creates an anonymous quotation and calls
it. This
is useful for small regexp style grammars:
"123" [EBNF digit=[0-9] => [[ digit> ]]
rule=digit+ EBNF] .
This produces 3-vector
V{ 1 2 3 }
I don't understand the parsing of the rule syntax itself between [EBNF and
EBNF]. "digit=[0-9]" and "rule=digit+" are rules strings without
whitespace. What is happening with the in-between "=> [[ digit> ]]"? This
looks like Factor (for making a vector) not EBNF, or a mixture of both
(quotation and "one or more").
I tried word inspect on the above vector. The inspect said "vector with 3
elements" and showed a grid with nine numbers. How is that?
Shaping
----------------------------------------------------------------------------
--
The Next 800 Companies to Lead America's Growth: New Video Whitepaper
David G. Thomson, author of the best-selling book "Blueprint to a
Billion" shares his insights and actions to help propel your
business during the next growth cycle. Listen Now!
http://p.sf.net/sfu/SAP-dev2dev
_______________________________________________
Factor-talk mailing list
Factor-talk@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/factor-talk
------------------------------------------------------------------------------
The Next 800 Companies to Lead America's Growth: New Video Whitepaper
David G. Thomson, author of the best-selling book "Blueprint to a
Billion" shares his insights and actions to help propel your
business during the next growth cycle. Listen Now!
http://p.sf.net/sfu/SAP-dev2dev
_______________________________________________
Factor-talk mailing list
Factor-talk@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/factor-talk
