42 lines
1,018 B
Ruby
42 lines
1,018 B
Ruby
# frozen_string_literal: true
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module Gitlab
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module Ci
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module Pipeline
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module Expression
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class Parser
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def initialize(tokens)
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@tokens = tokens.to_enum
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@nodes = []
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end
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##
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# This produces a reverse descent parse tree.
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#
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# It currently does not support precedence of operators.
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#
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def tree
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while token = @tokens.next
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case token.type
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when :operator
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token.build(@nodes.pop, tree).tap do |node|
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@nodes.push(node)
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end
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when :value
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token.build.tap do |leaf|
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@nodes.push(leaf)
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end
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end
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end
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rescue StopIteration
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@nodes.last || Lexeme::Null.new
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end
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def self.seed(statement)
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new(Expression::Lexer.new(statement).tokens)
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end
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end
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end
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end
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end
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end
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