101 lines
2.4 KiB
Ruby
101 lines
2.4 KiB
Ruby
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# A slice is a small part from the parse input. A slice mainly behaves like
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# any other string, except that it remembers where it came from (offset in
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# original input).
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#
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# == Extracting line and column
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#
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# Using the #line_and_column method, you can extract the line and column in
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# the original input where this slice starts.
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#
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# Example:
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# slice.line_and_column # => [1, 13]
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# slice.offset # => 12
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#
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# == Likeness to strings
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#
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# Parslet::Slice behaves in many ways like a Ruby String. This likeness
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# however is not complete - many of the myriad of operations String supports
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# are not yet in Slice. You can always extract the internal string instance by
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# calling #to_s.
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#
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# These omissions are somewhat intentional. Rather than maintaining a full
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# delegation, we opt for a partial emulation that gets the job done.
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#
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class Parslet::Slice
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attr_reader :str, :offset
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attr_reader :line_cache
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# Construct a slice using a string, an offset and an optional line cache.
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# The line cache should be able to answer to the #line_and_column message.
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#
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def initialize(string, offset, line_cache=nil)
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@str, @offset = string, offset
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@line_cache = line_cache
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end
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# Compares slices to other slices or strings.
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#
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def == other
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str == other
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end
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# Match regular expressions.
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#
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def match(regexp)
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str.match(regexp)
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end
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# Returns the slices size in characters.
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#
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def size
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str.size
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end
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# Concatenate two slices; it is assumed that the second slice begins
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# where the first one ends. The offset of the resulting slice is the same
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# as the one of this slice.
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#
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def +(other)
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self.class.new(str + other.to_s, offset, line_cache)
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end
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# Returns a <line, column> tuple referring to the original input.
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#
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def line_and_column
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raise ArgumentError, "No line cache was given, cannot infer line and column." \
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unless line_cache
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line_cache.line_and_column(self.offset)
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end
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# Conversion operators -----------------------------------------------------
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def to_str
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str
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end
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alias to_s to_str
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def to_slice
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self
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end
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def to_sym
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str.to_sym
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end
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def to_int
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Integer(str)
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end
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def to_i
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str.to_i
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end
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def to_f
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str.to_f
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end
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# Inspection & Debugging ---------------------------------------------------
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# Prints the slice as <code>"string"@offset</code>.
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def inspect
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str.inspect << "@#{offset}"
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end
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end
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