为不同元数的规则指定共同的语法动作

Question

我正在尝试为一个简单的 DSL 编写一个解析器，它有许多 <statementName> <param1> <param2> ... ; 形式的语句，其中参数的数量各不相同。由于语句的结构非常相似（都匹配语句名称字符串后跟一系列由名称给出的标记）并且生成的结果的结构非常相似（都存储语句名称和参数的散列），我想知道如何指定想要的结果结构，而不必为每个语句操作重复自己。

一个动作的伪代码 class 可以帮助我指定这样一个结果结构：

class FooActions {

  method *_stmt ($/) { 
    @result[0] = make string of statement name $/[0];
    @result[1] = make hash of $/[1..] with the keys being the name of the rule 
      at index (i.e. '"var"' for `<var=identifier>` and `"type"` for `<type>`, etc.) and 
      values being the `.made` results for the rules at index (see below);
    return @result;
  }

  method identifier ($/) { return ~$/ }

  method number ($/) { return +$/ }

  method type ($/) { return ~$/ }
}

测试文件：

use v6;
use Test;
use Foo;
my $s;
$s = 'GoTo 2 ;';
is_deeply Foo::FooGrammar.parse($s).made, ('GoTo', {pos => 2});
$s = 'Set foo 3 ;';
is_deeply Foo::FooGrammar.parse($s).made, ('Set', {var => 'foo', target => 3});
$s = 'Get bar Long ;';
is_deeply Foo::FooGrammar.parse($s).made, ('Get', {var => 'bar', type => 'Long'});
$s = 'Set foo bar ;';
is_deeply Foo::FooGrammar.parse($s).made, ('Set', {var => 'foo', target => 'bar'});

语法：

use v6;
unit package Foo;

grammar FooGrammar is export {
  rule TOP { <stmt> ';' }
  rule type { 'Long' | 'Int' }
  rule number { \d+ }
  rule identifier { <alpha> \w* }
  rule numberOrIdentifier { <number> || <identifier> }

  rule goto_stmt { 'GoTo' <pos=number> }
  rule set_stmt { 'Set' <var=identifier> <target=numberOrIdentifier> }
  rule get_stmt { 'Get' <var=identifier> <type> }
  rule stmt { <goto_stmt> || <set_stmt> || <get_stmt> }
}

Answer 1

此方法将每个语句类型表示为 Proto-regex and uses syms 以避免重复语句关键字（GoTo 等）。

单个语句没有操作方法。这些在下一级 (TOP) 处理，它在匹配上使用 caps 方法，将其转换为散列。

<sym>抓包用于额外关键字。行的其余部分转换为散列。解决方案如下：

语法和动作：

use v6;
unit package Foo;

grammar Grammar is export {
  rule TOP { <stmt> ';' }
  token type { 'Long' | 'Int' }
  token number { \d+ }
  token identifier { <alpha>\w* }
  rule numberOrIdentifier { <number> || <identifier> }

  proto rule stmt {*}
  rule stmt:sym<GoTo> { <sym> <pos=.number> }
  rule stmt:sym<Set>  { <sym> <var=.identifier> <target=.numberOrIdentifier> }
  rule stmt:sym<Get>  { <sym> <var=.identifier> <type> }
}

class Actions {
      method number($/)     { make +$/ }
      method identifier($/) { make ~$/ }
      method type($/)       { make ~$/ }
      method numberOrIdentifier($/)   { make ($<number> // $<identifier>).made }
      method TOP($/) {
          my %caps = $<stmt>.caps;
          my $keyw = .Str
              given %caps<sym>:delete;
          my %args = %caps.pairs.map: {.key => .value.made};
          make ($keyw,%args, );
      }
   }

测试：

use v6;
use Test;
use Foo;
my $actions = Foo::Actions.new;
my $s;
$s = 'GoTo 2 ;';
is-deeply Foo::Grammar.parse($s, :$actions).made, ('GoTo', {pos => 2});
$s = 'Set foo 3;';
is-deeply Foo::Grammar.parse($s, :$actions).made, ('Set', {var => 'foo', target => 3});
$s = 'Get bar Long ;';
is-deeply Foo::Grammar.parse($s, :$actions).made, ('Get', {var => 'bar', type => 'Long'});
$s = 'Set foo bar ;';
is-deeply Foo::Grammar.parse($s, :$actions).made, ('Set', {var => 'foo', target => 'bar'});

为不同元数的规则指定共同的语法动作

Specify common grammar actions for rules of different arity

parsing

raku