mirror of
https://github.com/mruby/mruby
synced 2026-06-08 16:11:16 +00:00
Yukihiro "Matz" Matsumoto
382 lines
8.7 KiB
Markdown
382 lines
8.7 KiB
Markdown
# NEWS for Lrama
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## Lrama 0.6.5 (2024-03-25)
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### Typed Midrule Actions
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User can specify the type of mid rule action by tag (`<bar>`) instead of specifying it with in an action.
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```
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primary: k_case expr_value terms?
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{
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$<val>$ = p->case_labels;
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p->case_labels = Qnil;
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}
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case_body
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k_end
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{
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...
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}
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```
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can be written as
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```
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primary: k_case expr_value terms?
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{
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$$ = p->case_labels;
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p->case_labels = Qnil;
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}<val>
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case_body
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k_end
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{
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...
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}
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```
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`%destructor` for midrule action is invoked only when tag is specified by Typed Midrule Actions.
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Difference from Bison's Typed Midrule Actions is that tag is postposed in Lrama however it's preposed in Bison.
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Bison supports this feature from 3.1.
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## Lrama 0.6.4 (2024-03-22)
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### Parameterizing rules (preceded, terminated, delimited)
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Support `preceded`, `terminated` and `delimited` rules.
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```
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program: preceded(opening, X)
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// Expanded to
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program: preceded_opening_X
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preceded_opening_X: opening X
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```
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```
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program: terminated(X, closing)
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// Expanded to
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program: terminated_X_closing
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terminated_X_closing: X closing
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```
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```
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program: delimited(opening, X, closing)
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// Expanded to
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program: delimited_opening_X_closing
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delimited_opening_X_closing: opening X closing
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```
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https://github.com/ruby/lrama/pull/382
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### Support `%destructor` declaration
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User can set codes for freeing semantic value resources by using `%destructor`.
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In general, these resources are freed by actions or after parsing.
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However if syntax error happens in parsing, these codes may not be executed.
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Codes associated to `%destructor` are executed when semantic value is popped from the stack by an error.
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```
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%token <val1> NUM
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%type <val2> expr2
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%type <val3> expr
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%destructor {
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printf("destructor for val1: %d\n", $$);
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} <val1> // printer for TAG
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%destructor {
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printf("destructor for val2: %d\n", $$);
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} <val2>
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%destructor {
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printf("destructor for expr: %d\n", $$);
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} expr // printer for symbol
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```
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Bison supports this feature from 1.75b.
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https://github.com/ruby/lrama/pull/385
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## Lrama 0.6.3 (2024-02-15)
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### Bring Your Own Stack
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Provide functionalities for Bring Your Own Stack.
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Ruby’s Ripper library requires their own semantic value stack to manage Ruby Objects returned by user defined callback method. Currently Ripper uses semantic value stack (`yyvsa`) which is used by parser to manage Node. This hack introduces some limitation on Ripper. For example, Ripper can not execute semantic analysis depending on Node structure.
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Lrama introduces two features to support another semantic value stack by parser generator users.
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1. Callback entry points
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User can emulate semantic value stack by these callbacks.
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Lrama provides these five callbacks. Registered functions are called when each event happen. For example %after-shift function is called when shift happens on original semantic value stack.
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- `%after-shift` function_name
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- `%before-reduce` function_name
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- `%after-reduce` function_name
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- `%after-shift-error-token` function_name
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- `%after-pop-stack` function_name
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2. `$:n` variable to access index of each grammar symbols
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User also needs to access semantic value of their stack in grammar action. `$:n` provides the way to access to it. `$:n` is translated to the minus index from the top of the stack.
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For example
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```
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primary: k_if expr_value then compstmt if_tail k_end
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{
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/*% ripper: if!($:2, $:4, $:5) %*/
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/* $:2 = -5, $:4 = -3, $:5 = -2. */
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}
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```
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https://github.com/ruby/lrama/pull/367
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## Lrama 0.6.2 (2024-01-27)
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### %no-stdlib directive
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If `%no-stdlib` directive is set, Lrama doesn't load Lrama standard library for
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parameterizing rules, stdlib.y.
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https://github.com/ruby/lrama/pull/344
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## Lrama 0.6.1 (2024-01-13)
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### Nested parameterizing rules
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Allow to pass an instantiated rule to other parameterizing rules.
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```
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%rule constant(X) : X
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;
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%rule option(Y) : /* empty */
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| Y
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;
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%%
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program : option(constant(number)) // Nested rule
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;
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%%
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```
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Allow to use nested parameterizing rules when define parameterizing rules.
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```
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%rule option(x) : /* empty */
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| X
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;
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%rule double(Y) : Y Y
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;
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%rule double_opt(A) : option(double(A)) // Nested rule
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;
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%%
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program : double_opt(number)
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;
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%%
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```
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https://github.com/ruby/lrama/pull/337
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## Lrama 0.6.0 (2023-12-25)
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### User defined parameterizing rules
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Allow to define parameterizing rule by `%rule` directive.
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```
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%rule pair(X, Y): X Y { $$ = $1 + $2; }
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;
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%%
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program: stmt
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;
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stmt: pair(ODD, EVEN) <num>
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| pair(EVEN, ODD) <num>
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;
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```
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https://github.com/ruby/lrama/pull/285
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## Lrama 0.5.11 (2023-12-02)
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### Type specification of parameterizing rules
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Allow to specify type of rules by specifying tag, `<i>` in below example.
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Tag is post-modification style.
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```
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%union {
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int i;
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}
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%%
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program : option(number) <i>
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| number_alias? <i>
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;
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```
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https://github.com/ruby/lrama/pull/272
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## Lrama 0.5.10 (2023-11-18)
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### Parameterizing rules (option, nonempty_list, list)
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Support function call style parameterizing rules for `option`, `nonempty_list` and `list`.
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https://github.com/ruby/lrama/pull/197
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### Parameterizing rules (separated_list)
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Support `separated_list` and `separated_nonempty_list` parameterizing rules.
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```
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program: separated_list(',', number)
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// Expanded to
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program: separated_list_number
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separated_list_number: ε
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separated_list_number: separated_nonempty_list_number
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separated_nonempty_list_number: number
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separated_nonempty_list_number: separated_nonempty_list_number ',' number
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```
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```
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program: separated_nonempty_list(',', number)
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// Expanded to
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program: separated_nonempty_list_number
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separated_nonempty_list_number: number
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separated_nonempty_list_number: separated_nonempty_list_number ',' number
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```
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https://github.com/ruby/lrama/pull/204
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## Lrama 0.5.9 (2023-11-05)
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### Parameterizing rules (suffix)
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Parameterizing rules are template of rules.
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It's very common pattern to write "list" grammar rule like:
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```
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opt_args: /* none */
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| args
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;
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args: arg
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| args arg
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```
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Lrama supports these suffixes:
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- `?`: option
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- `+`: nonempty list
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- `*`: list
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Idea of Parameterizing rules comes from Menhir LR(1) parser generator (https://gallium.inria.fr/~fpottier/menhir/manual.html#sec32).
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https://github.com/ruby/lrama/pull/181
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## Lrama 0.5.7 (2023-10-23)
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### Racc parser
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Replace Lrama's parser from hand written parser to LR parser generated by Racc.
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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).
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https://github.com/ruby/lrama/pull/62
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## Lrama 0.5.4 (2023-08-17)
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### Runtime configuration for error recovery
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Meke error recovery function configurable on runtime by two new macros.
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- `YYMAXREPAIR`: Expected to return max length of repair operations. `%parse-param` is passed to this function.
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- `YYERROR_RECOVERY_ENABLED`: Expected to return bool value to determine error recovery is enabled or not. `%parse-param` is passed to this function.
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https://github.com/ruby/lrama/pull/74
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## Lrama 0.5.3 (2023-08-05)
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### Error Recovery
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Support token insert base Error Recovery.
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`-e` option is needed to generate parser with error recovery functions.
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https://github.com/ruby/lrama/pull/44
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## Lrama 0.5.2 (2023-06-14)
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### Named References
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Instead of positional references like `$1` or `$$`,
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named references allow to access to symbol by name.
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```
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primary: k_class cpath superclass bodystmt k_end
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{
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$primary = new_class($cpath, $bodystmt, $superclass);
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}
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```
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Alias name can be declared.
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```
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expr[result]: expr[ex-left] '+' expr[ex.right]
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{
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$result = $[ex-left] + $[ex.right];
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}
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```
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Bison supports this feature from 2.5.
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### Add parse params to some macros and functions
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`%parse-param` are added to these macros and functions to remove ytab.sed hack from Ruby.
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- `YY_LOCATION_PRINT`
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- `YY_SYMBOL_PRINT`
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- `yy_stack_print`
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- `YY_STACK_PRINT`
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- `YY_REDUCE_PRINT`
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- `yysyntax_error`
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https://github.com/ruby/lrama/pull/40
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See also: https://github.com/ruby/ruby/pull/7807
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## Lrama 0.5.0 (2023-05-17)
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### stdin mode
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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.
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https://github.com/ruby/lrama/pull/8
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## Lrama 0.4.0 (2023-05-13)
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This is the first version migrated to Ruby.
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This version generates "parse.c" compatible with Bison 3.8.2.
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