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NEWS for Lrama

Lrama 0.6.0 (2023-12-25)

User defined parameterizing rules

Allow to define parameterizing rule by %rule directive.

%rule pair(X, Y): X Y { $$ = $1 + $2; }
                ;

%%

program: stmt
       ;

stmt: pair(ODD, EVEN) <num>
    | pair(EVEN, ODD) <num>
    ;

Lrama 0.5.11 (2023-12-02)

Type specification of parameterizing rules

Allow to specify type of rules by specifying tag, <i> in below example. Tag is post-modification style.

%union {
    int i;
}

%%

program         : option(number) <i>
                | number_alias? <i>
                ;

#272

Lrama 0.5.10 (2023-11-18)

Parameterizing rules (option, nonempty_list, list)

Support function call style parameterizing rules for option, nonempty_list and list.

#197

Parameterizing rules (separated_list)

Support separated_list and separated_nonempty_list parameterizing rules.

program: separated_list(',', number)

// Expanded to

program: separated_list_number
separated_list_number: ε
separated_list_number: separated_nonempty_list_number
separated_nonempty_list_number: number
separated_nonempty_list_number: separated_nonempty_list_number ',' number

program: separated_nonempty_list(',', number)

// Expanded to

program: separated_nonempty_list_number
separated_nonempty_list_number: number
separated_nonempty_list_number: separated_nonempty_list_number ',' number

#204

Lrama 0.5.9 (2023-11-05)

Parameterizing rules (suffix)

Parameterizing rules are template of rules. It's very common pattern to write "list" grammar rule like:

opt_args: /* none */
        | args
        ;

args: arg
    | args arg

Lrama supports these suffixes:

  • ?: option
  • +: nonempty list
  • *: list

Idea of Parameterizing rules comes from Menhir LR(1) parser generator (https://gallium.inria.fr/~fpottier/menhir/manual.html#sec32).

#181

Lrama 0.5.7 (2023-10-23)

Racc parser

Replace Lrama's parser from hand written parser to LR parser generated by Racc. Lrama uses --embedded option to generate LR parser because Racc is changed from default gem to bundled gem by Ruby 3.3 (#132).

#62

Lrama 0.5.4 (2023-08-17)

Runtime configuration for error recovery

Meke error recovery function configurable on runtime by two new macros.

  • YYMAXREPAIR: Expected to return max length of repair operations. %parse-param is passed to this function.
  • YYERROR_RECOVERY_ENABLED: Expected to return bool value to determine error recovery is enabled or not. %parse-param is passed to this function.

#74

Lrama 0.5.3 (2023-08-05)

Error Recovery

Support token insert base Error Recovery. -e option is needed to generate parser with error recovery functions.

#44

Lrama 0.5.2 (2023-06-14)

Named References

Instead of positional references like $1 or $$, named references allow to access to symbol by name.

primary: k_class cpath superclass bodystmt k_end
           {
             $primary = new_class($cpath, $bodystmt, $superclass);
           }

Alias name can be declared.

expr[result]: expr[ex-left] '+' expr[ex.right]
                {
                  $result = $[ex-left] + $[ex.right];
                }

Bison supports this feature from 2.5.

Add parse params to some macros and functions

%parse-param are added to these macros and functions to remove ytab.sed hack from Ruby.

  • YY_LOCATION_PRINT
  • YY_SYMBOL_PRINT
  • yy_stack_print
  • YY_STACK_PRINT
  • YY_REDUCE_PRINT
  • yysyntax_error

#40

See also: ruby/ruby#7807

Lrama 0.5.0 (2023-05-17)

stdin mode

When - is given as grammar file name, reads the grammar source from STDIN, and takes the next argument as the input file name. This mode helps pre-process a grammar source.

#8

Lrama 0.4.0 (2023-05-13)

This is the first version migrated to Ruby. This version generates "parse.c" compatible with Bison 3.8.2.