brace-expansion.p6

grammar BraceExpansion {
    token TOP { ( <.normalchar>+ | <alt> )* }
    token normalchar { \\. | <-[ { , } ]> }
    token alt { 
	'{' ~ '}' <TOP>* % \, 
    }
}
 
sub crosswalk($/) {
    [X~] $0.map: -> $/ { [$<alt><TOP>».&crosswalk] or ~$/ }
}
 
sub brace-expand($s) { crosswalk BraceExpansion.parse($s) }


sub bxtest(*@s) {
    for @s -> $s {
        say "\n$s";
        for brace-expand($s) {
            say "    ", $_;
        }
    }
}
 
bxtest Q:to/END/.lines;
    ~/{Downloads,Pictures}/*.{jpg,gif,png}
    It{{em,alic}iz,erat}e{d,}, please.
    {,{,gotta have{ ,\, again\, }}more }cowbell!
    {}} some {\\{edge,edgy} }{ cases, here\\\}
    a{b{1,2}c
    a{1,2}b}c
    a{1,{2},3}b
    a{b{1,2}c{}}
    END