51 lines
1.1 KiB
Ruby
51 lines
1.1 KiB
Ruby
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# Allows specifying rules as strings using the exact same grammar that treetop
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# does, minus the actions. This is on one hand a good example of a fully
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# fledged parser and on the other hand might even turn out really useful.
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#
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# This can be viewed as an extension to parslet and might even be hosted in
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# its own gem one fine day.
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#
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class Parslet::Expression
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include Parslet
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autoload :Treetop, 'parslet/expression/treetop'
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# Creates a parslet from a foreign language expression.
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#
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# Example:
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#
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# Parslet::Expression.new("'a' 'b'")
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#
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def initialize(str, opts={}, context=self)
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@type = opts[:type] || :treetop
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@exp = str
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@parslet = transform(
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parse(str))
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end
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# Transforms the parse tree into a parslet expression.
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#
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def transform(tree)
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transform = Treetop::Transform.new
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# pp tree
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transform.apply(tree)
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rescue
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warn "Could not transform: " + tree.inspect
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raise
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end
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# Parses the string and returns a parse tree.
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#
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def parse(str)
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parser = Treetop::Parser.new
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parser.parse(str)
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end
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# Turns this expression into a parslet.
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#
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def to_parslet
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@parslet
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end
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end
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