vendored parslet, deemed stable enough and better without dependency

lib/parslet/slice.rb

@@ -0,0 +1,101 @@
+
+# A slice is a small part from the parse input. A slice mainly behaves like
+# any other string, except that it remembers where it came from (offset in
+# original input).
+#
+# == Extracting line and column
+#
+# Using the #line_and_column method, you can extract the line and column in
+# the original input where this slice starts.
+#
+# Example:
+#   slice.line_and_column # => [1, 13]
+#   slice.offset          # => 12
+#
+# == Likeness to strings
+#
+# Parslet::Slice behaves in many ways like a Ruby String. This likeness
+# however is not complete - many of the myriad of operations String supports
+# are not yet in Slice. You can always extract the internal string instance by
+# calling #to_s.
+#
+# These omissions are somewhat intentional. Rather than maintaining a full
+# delegation, we opt for a partial emulation that gets the job done.
+#
+class Parslet::Slice
+  attr_reader :str, :offset
+  attr_reader :line_cache
+
+  # Construct a slice using a string, an offset and an optional line cache. 
+  # The line cache should be able to answer to the #line_and_column message. 
+  #
+  def initialize(string, offset, line_cache=nil)
+    @str, @offset = string, offset
+    @line_cache = line_cache
+  end
+
+  # Compares slices to other slices or strings.
+  #
+  def == other
+    str == other
+  end
+
+  # Match regular expressions.
+  #
+  def match(regexp)
+    str.match(regexp)
+  end
+
+  # Returns the slices size in characters.
+  #
+  def size
+    str.size
+  end
+  
+  # Concatenate two slices; it is assumed that the second slice begins 
+  # where the first one ends. The offset of the resulting slice is the same
+  # as the one of this slice. 
+  #
+  def +(other)
+    self.class.new(str + other.to_s, offset, line_cache)
+  end
+
+  # Returns a <line, column> tuple referring to the original input.
+  #
+  def line_and_column
+    raise ArgumentError, "No line cache was given, cannot infer line and column." \
+      unless line_cache
+
+    line_cache.line_and_column(self.offset)
+  end
+
+
+  # Conversion operators -----------------------------------------------------
+  def to_str
+    str
+  end
+  alias to_s to_str
+
+  def to_slice
+    self
+  end
+  def to_sym
+    str.to_sym
+  end
+  def to_int
+    Integer(str)
+  end
+  def to_i
+    str.to_i
+  end
+  def to_f
+    str.to_f
+  end
+
+  # Inspection & Debugging ---------------------------------------------------
+
+  # Prints the slice as <code>"string"@offset</code>.
+  def inspect
+    str.inspect << "@#{offset}"
+  end
+end