# 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>
                ;
```

https://github.com/ruby/lrama/pull/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`.

https://github.com/ruby/lrama/pull/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
```

https://github.com/ruby/lrama/pull/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).

https://github.com/ruby/lrama/pull/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 (https://github.com/ruby/lrama/pull/132).

https://github.com/ruby/lrama/pull/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.

https://github.com/ruby/lrama/pull/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.

https://github.com/ruby/lrama/pull/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`

https://github.com/ruby/lrama/pull/40

See also: https://github.com/ruby/ruby/pull/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.

https://github.com/ruby/lrama/pull/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.