gistfile1.txt

#!/opt/rakudo-star-2016.10/bin/perl6
use v6;


#############################################################################################
# The result of this perl6 program depends on the usage of "use Grammar::Tracer;" instruction.
#
# If "use Grammar::Tracer;" is active the program display :
# 
#｢;DECODE(CODUO,'C',UFO_IDE,'')｣
# main => ｢;DECODE(CODUO,'C',UFO_IDE,'')｣
#  text => ｢;｣
#  decode => ｢DECODE(CODUO,'C',UFO_IDE,'')｣
#   decodeinstr => ｢DECODE｣
#   paraIn => ｢(｣
#   val => ｢CODUO｣
#    expr => ｢CODUO｣
#     mot1 => ｢CODUO｣
#   whenthen => ｢,'C',UFO_IDE｣
#    comma => ｢,｣
#    when => ｢'C'｣
#     expr => ｢'C'｣
#      mot1 => ｢'｣
#      mot1 => ｢C｣
#      mot1 => ｢'｣
#    comma => ｢,｣
#    then => ｢UFO_IDE｣
#     expr => ｢UFO_IDE｣
#      mot1 => ｢UFO_IDE｣
#   comma => ｢,｣
#   else => ｢''｣
#    expr => ｢''｣
#     mot1 => ｢'｣
#     mot1 => ｢'｣
#   paraOut => ｢)｣
#
# If "use Grammar::Tracer;" is not active the program display 
#
#｢;DECODE(CODUO,'C',UFO_IDE,'')｣
# textfin => ｢;DECODE(CODUO,'C',UFO_IDE,'')｣
#
# I'm not sure to well understand why and not sure it's a "normal" behaviour ...
#############################################################################################

use Grammar::Tracer;
 
grammar DECODE {
 
    rule  TOPDECODE     { [<main>]* [<textfin>]? }
      rule  main     { <text> <decode> }
        rule  decode {:i <decodeinstr> <paraIn> <val> <whenthen>+ [<comma> <else>]? <paraOut> } 
          regex decodeinstr {:i 'decode'\s* }
          regex val    {:s <decode>
                           |<expr> }
          regex  whenthen {:i <comma> <when> <comma> <then> }
            regex when    {:s <decode>
                             | <expr> }
            regex then    {:s <decode>
                             |<expr> }
            regex else    {:s <decode>
                             |<expr> }
        regex text    {:s .+? }
      regex textfin {:s .+ }
      regex comma   {\s*','\s* }
      regex paraIn  {\s*'('\s*}
      regex paraOut {\s*')'\s*}
      token ws { <!ww> }
      regex expr  {:s {}<mot1>*
      #regex expr  {:s <mot1>*
                      | [<mot1><paraIn><mot>*<paraOut>]*
                      | [<paraIn><mot>*<paraOut>]*
                  }
      rule mot  { <-[()]>+?  }
      rule mot1  { <-[(),]>+?  }
}
 
 
 
my $cbl = "\;DECODE(CODUO,'C',UFO_IDE,'')" ;
say DECODE.parse($cbl, rule => 'TOPDECODE');