Module: Jade::Parsing::Combinators

Extended by:
Dsl
Included in:
Jade::Parsing, Symbol::Parser
Defined in:
lib/jade/parsing/combinators.rb

Defined Under Namespace

Modules: Dsl Classes: CommaList, P, State

Instance Method Summary collapse

Methods included from Dsl

parser

Instance Method Details

#at_least_one(parser, separated_by: none.skip) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 25

def at_least_one(parser, separated_by: none.skip)
  tail = separated_by >> sequence(parser, separated_by:)
  parser >> optional(tail, default: [])
end

#comma_sequence(parser) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 53

def comma_sequence(parser)
  inner = sequence(parser, separated_by: type(:comma).skip)
  P.new do |state|
    inner.call(state).and_then do |(items, state1)|
      trailing, state2 =
        if !state1.eof? && state1.current.type == :comma
          [true, state1.advance]
        else
          [false, state1]
        end

      Ok[[CommaList.new(items:, trailing_comma: trailing), state2]]
    end
  end
end

#grouped(parser) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 21

def grouped(parser)
  type(:lparen).skip >> parser >> type(:rparen).skip
end

#lazy(&block) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 169

def lazy(&block)
  P.new do |input|
    block.call.call(input)
  end
end

#many(parser) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 107

def many(parser)
  P.new do |state|
    oks = []
    current = state
    committed_err = nil

    loop do
      break if current.eof?

      case parser.call(current)
      in Ok([value, next_state])
        oks << value
        current = next_state
      in Err([err, err_state])
        committed_err = Err[[err, err_state]] if err.committed?
        break
      end
    end

    committed_err || Ok[[oks, current]]
  end
end

#maybe(parser) ⇒ Object

Consume ‘parser` if it matches; if not, drop the slot from the surrounding `>>` tuple (no value, no failure).



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# File 'lib/jade/parsing/combinators.rb', line 32

def maybe(parser)
  (parser | none).skip
end

#optional(parser, default: nil) ⇒ Object

Consume ‘parser` if it matches; otherwise inject `default` as the value. Keeps tuple arity stable in `>>` chains.



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# File 'lib/jade/parsing/combinators.rb', line 38

def optional(parser, default: nil)
  parser | none.map { default }
end

#recovering_sequence(parser, sync_types:) ⇒ Object

Tolerant counterpart of ‘sequence`. Strict mode (the default) behaves identically; tolerant mode records a diagnostic and resumes at the next sync token instead of failing.



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# File 'lib/jade/parsing/combinators.rb', line 77

def recovering_sequence(parser, sync_types:)
  P.new { recovering_step(parser, sync_types, it, []) }
end

#recovering_step(parser, sync_types, state, results) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 81

def recovering_step(parser, sync_types, state, results)
  return Ok[[results, state]] if state.eof?

  case parser.call(state)
  in Ok([value, next_state])
    recovering_step(parser, sync_types, next_state, [*results, value])

  in Err([err, err_state]) unless state.tolerant
    err.committed? ? Err[[err, err_state]] : Ok[[results, state]]

  in Err([err, err_state])
    # Always advance at least one token so termination is guaranteed
    # even when sync_types isn't ahead.
    moved_past = err.committed? && err_state.position > state.position
    recovered = (moved_past ? err_state : state.advance)
      .skip_until(sync_types)
      .add_diagnostic(err.to_diagnostic)

    recovering_step(parser, sync_types, recovered, results)
  end
end

#sequence(parser, separated_by: none.skip) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 42

def sequence(parser, separated_by: none.skip)
  (parser.map { [it] } >> many(separated_by >> parser))
    .map { it.flatten(1) }
end

#skip(parser) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 103

def skip(parser)
  parser.map { |_| :skip }
end

#type(type) ⇒ Object 



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# File 'lib/jade/parsing/combinators.rb', line 130

def type(type)
  (@types ||= {})[type] ||= P.new do |state|
    if state.eof?
      Err[[
        Parsing::EOFError.new(
          entry:    state.entry,
          span:     nil,
          expected: type,
        ),
        state,
      ]]

    elsif state.current.type == :invalid_op
      Err[[
        Parsing::InvalidOperatorError.new(
          entry:    state.entry,
          span:     state.current.range,
          actual:   state.current,
        ),
        state,
      ]]

    elsif state.current.type == type
      Ok[([state.current, state.advance])]

    else
      Err[[
        Parsing::UnexpectedTokenError.new(
          entry:    state.entry,
          span:     state.current.range,
          actual:   state.current,
          expected: type,
        ),
        state,
      ]]
    end
  end
end