In a presentation I saw a little calculator written in NQP that read
from and write to the commandline. How can I parse (compile) a string
and assign the result from the grammar action to a variable with a
NQP-program. Is it possible?
# parser
grammar ABC::Grammar {
rule TOP { <expr> }
rule expr { <integer> <addop> <integer> };
token addop { '+' | '-' }
token integer { \d+ }
}
# transform to ast
class ABC::Actions {
method TOP($/) {
make PAST::Block.new( $<expr>.ast );
}
method expr($/) {
my $pirop := $<addop> eq '-' ?? 'sub' !! 'add';
make PAST::Op.new( :pirop($pirop),
+$<integer>[0], +$<integer>[1]);
}
}
# compiler object (HLL::Compiler is base class for compilers)
class ABC::Compiler is HLL::Compiler {
ABC::Compiler.language('abc');
ABC::Compiler.parsegrammar(ABC::Grammar);
ABC::Compiler.parseactions(ABC::Actions);
}
# invoke the compiler
my @ARGS := (pir::getinterp__p)[2]; # args from Parrot
ABC::Compiler.command_line(@ARGS);
#my $result := ....( '3+4' ) ???
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