vendored parslet, deemed stable enough and better without dependency

lib/parslet/atoms/str.rb

@@ -0,0 +1,39 @@
+# Matches a string of characters. 
+#
+# Example: 
+# 
+#   str('foo') # matches 'foo'
+#
+class Parslet::Atoms::Str < Parslet::Atoms::Base
+  attr_reader :str
+  def initialize(str)
+    super()
+
+    @str = str.to_s
+    @pat = Regexp.new(Regexp.escape(str))
+    @len = str.size
+    @error_msgs = {
+      :premature  => "Premature end of input", 
+      :failed     => "Expected #{str.inspect}, but got "
+    }
+  end
+  
+  def try(source, context, consume_all)
+    return succ(source.consume(@len)) if source.matches?(@pat)
+    
+    # Input ending early:
+    return context.err(self, source, @error_msgs[:premature]) \
+      if source.chars_left<@len
+    
+    # Expected something, but got something else instead:  
+    error_pos = source.pos  
+    return context.err_at(
+      self, source, 
+      [@error_msgs[:failed], source.consume(@len)], error_pos) 
+  end
+  
+  def to_s_inner(prec)
+    "'#{str}'"
+  end
+end
+