#!perl6
#
# test-grammar.pl6:
# 
# Attempted to specify a grammar with a string evaluated during the script execution
# at run-time depending on input from another process.  Below was written to show
# how and why it doesn't yet do what you mean.
#
# Short-term strategy is: write a parsing dispatch table which determines
# which type of known grammars are being used and parses against the
# specified grammar.  (Not listed in this example.)
#
# WARNING: the below is meant to show Perl6 code which is a BAD EXAMPLE.
#

our grammar	Example::Grammar;	# Grammar to be evaluated
our Match	$match;			# Match object
our Str		$grammar;		# Str containing grammar
our Str		$string  =
    "parse me fully";			# Str to parse


## PASS:{ # Works - but only due to the string being declared versus eval ##
# 0. Literal string encapsulation of grammar
$grammar = "grammar Example::Grammar {
	rule TOP { <wordlist> }
	token wordlist { [<word> \s*]+ }
	regex word {\w+}
}";
say  "# Grammar:\n|$grammar|";
eval($grammar); ## <-- Not required.. since Perl6 gets it from string above -

## No wonder it cannot be passed from the other process in a string:
## Well duh. (say returns interpreted rules in the grammar, rather than
## delaring the Grammar block) finding an interpolated code block in
## the double-quoted String, not the original Str of $grammar
##
## Change above to single quotes, fails.
##

## } ##


## FAILS:{ # Seemingly Dubious ##
our $grams = q/
	rule TOP { <wordlist> }
	token wordlist { [<word> \s*]+ }
	regex word {\w+}
/;
#
## 1. Basic string concat to nest target rules inside grammar block:
#our Str	$gram_1 = 'grammar Example::Grammar {';
#$gram_1 ~= $grams;
#$gram_1 ~= '}';
#say "# Grammar 1:\n|$gram_1|";
#eval($gram_1); # FAIL_1
#
## 2. Basic string interpolation to nest target rules inside grammar block:
##our Str   $gram_2 = "grammar Example::Grammar {$grams}";
#our Str   $gram_2 = "grammar Example::Grammar \{$grams\}";
#say "# Grammar 2:\n|$gram_2|";
#eval($gram_2); # FAIL_2 - still fails
#
## 3. Inclusion in grammar statement:
#our grammar Example::Grammar {
#	<$grams>
#};	# FAIL_3 - either with :: or with-out inside <> or outside, doesn't matter
#

## } ##


#
# @eval(Str $string, Str $grammar --> Match $match):
#

#eval(q%

say "TEST: ";
$match = Example::Grammar.parse($string);
say " 1. perl: ",$match.perl;
say " 2. string map: ";

#
# Match and print a wordlist using test grammar:
#
#say map{~$_},$word;
for ($match<wordlist><word>) -> @w {
    for (@w) -> $W {
      say "|" ~ $W ~ "|";
    }
}

#%);


##
## TODO: OK then, how do you eval a grammar?
##