Mutable buffer to construct ropes.

create n returns a fresh buffer, initially empty. The n parameter is the initial size of the internal rope that holds the buffer contents. The buffer will grow dynamically to accomodate new inputs.

Empty the buffer.

Empty the buffer.

Return the number of characters currently contained in the buffer.

add_char b c appends the character c at the end of the buffer b.

• raises Failure

  if the length if the buffer exceeds max_int.

add_string b s appends the string s at the end of the buffer b.

• raises Failure

  if the length if the buffer exceeds max_int.

add_substring b s ofs len takes len characters from offset ofs in string s and appends them at the end of the buffer b.

• raises Invalid_argument

  if ofs and len do not designate a valid substring of s.

• raises Failure

  if the length if the buffer exceeds max_int.

add_rope b r add the rope r to the buffer b.

add_channel b ic n reads exactly n characters from the input channel ic and stores them at the end of buffer b.

• raises End_of_file

  if the channel contains fewer than n characters.

add_buffer b1 b2 appends the current contents of buffer b2 at the end of buffer b1. b2 is not modified.

Return a copy of the current contents of the buffer. The buffer itself is unchanged.

sub b off len returns a rope of the current contents of the buffer b starting at offset off of length len bytes. The buffer itself is unaffected.

• raises Invalid_argument

  if out of bounds request.

nth b i returns the ith character if the buffer.

• raises Out_of_bounds

  if i < 0 or i >= length b. Time: O(log(length b)).