Hi there!
I need to wite a parser. I tried to do it using the pegs module. I wrote my
grammar and it works, it recognizez strings. But now I need to write some
actions to actually build a syntactic tree while parsing. I need to access the
captured portions while parsing. Something like:
import strutils, pegs
let grammar = peg """
terms <- ^ term+ $
term <- \letter* {\d+} \n+
"""
let example = """a1
b2
c3
"""
let parseExample = grammar.eventParser:
pkNonTerminal:
enter: # p, s, start
if p.nt.name=="term":
echo " It seems like a new term, let's check it..."
leave: # p, s, start, length (length = -1 in case of failure)
if p.nt.name=="term" and length >= 1:
echo "Yes indeed, it's a term and I captured this: '", $1, "'"
let pLen = parseExample(example)
echo pLen
Run
The result is:
It seems like a new term, let's check it...
Yes indeed, it's a term and I captured this: '1'
It seems like a new term, let's check it...
Yes indeed, it's a term and I captured this: '1'
It seems like a new term, let's check it...
Yes indeed, it's a term and I captured this: '1'
It seems like a new term, let's check it...
9
Run
Obviously, $1 is not understood as "the first captured string", but as the
string representation of a literal 1.
How can I access the captured strings for use in the enter/leave procs?
PS: Maybe I'm doing it wrong. I intend to use the whole grammar (about 20-30
rules) to parse a file in one shot. Is this approach OK?
