meta generation of macros

meta_macros.rs

use paste::paste;

macro_rules! get_char_len {
  ($x:tt) => {
    stringify!($x).len()
  }
}

macro_rules! one {
  $(x:tt) => {
    1
  }
}

macro_rules! meta_def_generator_dd {
  (
    $name:ident | 
    { 
      $( 
        ( $($meta_matcher_dd:tt)* ) => { $($meta_body_dd:tt)* }
      );+ 
    } | 
    $bang:tt | $d:tt 
  ) => {
    macro_rules $bang $name {
      $( 
        ( $($meta_matcher)* ) => { $($meta_body)* }
      );+ 
    } 
  }
}

macro_rules! meta_counter_def {
  ( $name:ident ) => {
    meta_def_generator_dd!( 
      $name:ident |
      {
        // ( () | ( $($current:tt)* ) | [ $map:ident ] )
        ( () | ( $dd ($dd current:tt)* ) | [ $dd map:ident ] ) => {
          vec![$dd ($dd current)*]
        };
        // ( ( $first:tt $( $rest:tt )* ) | ( $($current:tt)* ) | [ $map:ident ] )
        ( ( $dd first:tt $dd ( $dd rest:tt )* ) | ( $dd ($dd current:tt)* ) | [ $dd map:ident ] ) => {
          counter!( ( $dd ( $dd rest )* ) | $dd map!($dd first) + $dd ($dd current)* )
        };
        // ( ( $first:tt $( $rest:tt )* ) | [ $map:ident ] )
        ( ( $dd first:tt $dd ( $dd rest:tt )* ) | [ $dd map:ident ] ) => {
          counter!( ( $dd ( $dd rest )* ) | $dd map!($dd first) )
        };
      } |
      ! | $
    )
  }
}

macro_rules! meta_generate {
  ( $macro_meta_def:ident, $name:ident ) => {
    $macro_meta_def!($name)
  }
}

macro_rules! meta_call_with_dollar {
  ( ( $macro_name:ident, $($args:tt)* ) | $bang:tt ) => {
    [< _ $macro_name >] ! ( $($args:tt)* | $)
  }
}


macro_rules! meta_generate_then_call {
  ( $macro_name:ident, $meta_macro_def:ident, $($args:tt)* ) => {
    meta_generate( $meta_macro_def | ! | $ )
    meta_call_with_dollar( $macro_name, $($args:tt)* )
  }
}

macro_rules! generate {
  ( $macro_generator:ident, $macro_name:ident, $($args:tt)* ) => {
    $macro_generator!( $($args:tt)* | ! | $ );
  }
}

macro_rules! call_with_dollar {
  ( $macro_name:ident, $($args:tt)* ) => {
    [< _ $macro_name >]!($($args:tt)* | $)
  }
}

macro_rules! counter {
  ( () | $($current:tt)* $([ $map:ident ])? ) => {
    vec![$($current)*]
  };
  ( ( $first:tt $( $rest:tt )* ) | $($current:tt)* | $([ $map:ident ])? ) => {
      counter!( ( $( $rest )* ) | $map!($first), $($current)* )
  };
  ( ( $first:tt $( $rest:tt )* ) ) => {
    counter!( ( $( $rest )* ) | get_char_len!($first) )
  };
}

macro_rules! count_len {
  ($($input:tt)*) => {
    fn tally_count() -> usize {
      counter!( ($($input)*) )
    }
    println!("\"{}\" has {} token-trees", stringify!($($input)*), tally_count() );
  }
}


// macro_rules! cascade1 {
//   ( ($($paste_start:tt)*), ($($paste_end:tt)*) | $d:tt ) => {
//     macro_rules! cascade_final {
//       () => {
//         println!(stringify!($d $($paste_start:tt)* $var _world ($($paste_end:tt)*) ));
//       }
//     }
//   }
// }

// macro_rules! cascade0 {
//   ( $var:ident ) => {
//     cascade1!($);
//   }
// }

fn main() {
  // cascade0!(hello);
  // count_len!(hello);
  tester!()
}