I've posted some things previously on this topic - but in short, you don't really need to use events to do this. It's possible to do it in a semi-straightforward fashion without a lot of jumping through hoops (just a bunch of rules).
Here's some grammar fragments demonstrating what I'm talking about (this handles single quoted, double quoted, and "quote-like" parsing (e.g. q%%, q||), while efficiently handling simple quoted strings that have no escape sequences but falling back to an escape-aware mode when they're present. my ($dsl, $grammar) = <<'==================================================================================================='; :default ::= action => [values] lexeme default = latm => 1 [...] # Normal, bare, unquoted value ::= value_n value_n ::= valword_n # Quoted but not escaped # reassemble action value ::= value_qd action => val_qd | value_qs action => val_qs | value_ql0 action => val_ql0 | value_ql1 action => val_ql1 value_qd ::= valword_qd value_qs ::= valword_qs value_ql0 ::= valword_ql0 value_ql1 ::= valword_ql1 # Quoted and escaped # reassemble action value ::= (g_quote_d) value_eqd (g_quote_d) action => val_eqd | (g_quote_s) value_eqs (g_quote_s) action => val_eqs | (g_quote_ls0) value_eql0 (g_quote_le0) action => val_eql0 | (g_quote_ls1) value_eql1 (g_quote_le1) action => val_eql1 value_eqd ::= valword_eqd* value_eqs ::= valword_eqs* value_eql0 ::= valword_eql0* value_eql1 ::= valword_eql1* # Normal, bare, unquoted valword_n ~ valword_n_c valword_n_c ~ [\w_\@:.\/\*-]+ # Quoted but not escaped valword_qd ~ quote_d valword_qd_c quote_d valword_qs ~ quote_s valword_qs_c quote_s valword_ql0 ~ quote_ls0 valword_ql0_c quote_le0 valword_ql1 ~ quote_ls1 valword_ql1_c quote_le1 valword_qd_c ~ [^"\\]* valword_qs_c ~ [^'\\]* valword_ql0_c ~ [^|\\]* valword_ql1_c ~ [^%\\]* # Quoted and escaped valword_eqd ~ valword_eqd_c valword_eqs ~ valword_eqs_c valword_eql0 ~ valword_eql0_c valword_eql1 ~ valword_eql1_c valword_eqd_c ~ [^"] | whitespace | escape ["] valword_eqs_c ~ [^'] | whitespace | escape ['] valword_eql0_c ~ [^|] | whitespace | escape [|] valword_eql1_c ~ [^%] | whitespace | escape [%] # These do translation, but cannot be enabled yet as the expectation is no translation. # valword_eqd ~ [^\a\b\e\f\r\n\t\\"] | whitespace | escape valword_esc # valword_eqs ~ [^\a\b\e\f\r\n\t\\'] | whitespace | escape valword_esc # valword_esc ~ [abefrnt\\"'] # The same base lexemes cannot be directly used by both the lexer and grammar *at the same time*. # Work around it by providing wrapper lexeme rules for the grammar which end up at the same terminal. g_quote_d ~ quote_d g_quote_s ~ quote_s g_quote_ls0 ~ quote_ls0 g_quote_le0 ~ quote_le0 g_quote_ls1 ~ quote_ls1 g_quote_le1 ~ quote_le1 quote_d ~ ["] quote_s ~ ['] quote_ls0 ~ 'q|' quote_le0 ~ '|' quote_ls1 ~ 'q%' quote_le1 ~ '%' escape ~ '\' :discard ~ whitespace whitespace ~ [\s]+ =================================================================================================== # Deescaping table my $xtab = { 'eqd' => { q(\") => qq(") }, 'eqs' => { q(\') => qq(') }, 'eql0' => { q(\|) => qq(|) }, 'eql1' => { q(\%) => qq(%) }, # # Not presently used. # 'eqx' => { # q(\a) => qq(\a), # q(\b) => qq(\b), # q(\e) => qq(\e), # q(\f) => qq(\f), # q(\n) => qq(\n), # q(\r) => qq(\r), # q(\t) => qq(\t), # q(\") => qq("), # q(\') => qq('), # q(\\\\) => qq(\\), # }, }; # Deescaping functions sub val_eqd { return [ join '', map +($xtab->{'eqd'}{$_} || $_), @{$_[1]} ] } sub val_eqs { return [ join '', map +($xtab->{'eqs'}{$_} || $_), @{$_[1]} ] } sub val_eql0 { return [ join '', map +($xtab->{'eql0'}{$_} || $_), @{$_[1]} ] } sub val_eql1 { return [ join '', map +($xtab->{'eql1'}{$_} || $_), @{$_[1]} ] } #sub val_eqx { return [ join '', map +($xtab->{'eqx'}{$_} || $_), @{$_[1]} ] } # Dequoting functions sub val_qd { return [ substr($_[1]->[0], 1, -1) ] } sub val_qs { return [ substr($_[1]->[0], 1, -1) ] } sub val_ql0 { return [ substr($_[1]->[0], 2, -1) ] } sub val_ql1 { return [ substr($_[1]->[0], 2, -1) ] } The "deescape anything back to it's original form" isn't used in the above, but simply commented out. The approach would be the same. -cl On Sep 22, 2014, at 0012 PT, Ron Savage <r...@savage.net.au> wrote: > I've developed a grammar (with help from various people of course) for quoted > strings: http://scsys.co.uk:8002/424926 > > Requirements: > > o Strings must be quoted > > o Strings are either single or double quoted > > o The escape character is \ > > o If the string is single quoted, internal single quotes must be escaped > > o If the string is double quoted, internal double quotes must be escaped > > o Any other character may be escaped > > o If a character is escaped, the escape character is preserved in the output > > o Empty strings are accepted -- You received this message because you are subscribed to the Google Groups "marpa parser" group. To unsubscribe from this group and stop receiving emails from it, send an email to marpa-parser+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.