On Jan 23, 4:12 am, Steven D'Aprano <st...@remove-this-
cybersource.com.au> wrote:
>
>
> An alternative would be to do exactly what you want lists to do: track
> the start of the list. Untested:
>
> def recurse(prefix_lines):
> start = 0
> end = len(prefix_lines)
> while start < end:
> prefix, line = prefix_lines[start]
> if line == '':
> start += 1
> append('')
> else:
> block_size = get_block(prefix_lines)
> if block_size == 1:
> start += 1
> if line == pass_syntax:
> pass
> elif line.startswith(flush_left_syntax):
> append(line[len(flush_left_syntax):])
> elif line.startswith(flush_left_empty_line):
> append('')
> else:
> append(prefix + leaf_method(line))
> else:
> block = prefix_lines[:block_size]
> start = block_size
> branch_method(output, block, recurse)
> return
>
> No more O(N) deletions. Problem solved.
>
A minor modification of your solution does work, but it also slightly
+ complicates the implementation. Keeping track of the start variable
requires bookkeeping not just in recurse(), but also in methods that
it calls. This is a pretty small program, so it's acceptable to pass
around an offset variable to anybody else who might want to be
consuming the list.
############ Generic indentation stuff follows
-def get_indented_block(prefix_lines):
- prefix, line = prefix_lines[0]
+def get_indented_block(prefix_lines, start):
+ prefix, line = prefix_lines[start]
len_prefix = len(prefix)
i = 1
- while i < len(prefix_lines):
- new_prefix, line = prefix_lines[i]
+ while i + start < len(prefix_lines):
+ new_prefix, line = prefix_lines[start+i]
if line and len(new_prefix) <= len_prefix:
break
i += 1
- while i-1 > 0 and prefix_lines[i-1][1] == '':
+ while i-1 > 0 and prefix_lines[start+i-1][1] == '':
i -= 1
return i
@@ -190,15 +190,16 @@
):
append = output.append
def recurse(prefix_lines):
- while prefix_lines:
- prefix, line = prefix_lines[0]
+ start = 0
+ while start < len(prefix_lines):
+ prefix, line = prefix_lines[start]
if line == '':
- prefix_lines.pop(0)
+ start += 1
append('')
else:
- block_size = get_block(prefix_lines)
+ block_size = get_block(prefix_lines, start)
if block_size == 1:
- prefix_lines.pop(0)
+ start += 1
if line == pass_syntax:
pass
elif line.startswith(flush_left_syntax):
@@ -208,8 +209,8 @@
else:
append(prefix + leaf_method(line))
else:
- block = prefix_lines[:block_size]
- prefix_lines = prefix_lines[block_size:]
+ block = prefix_lines[start:start+block_size]
+ start += block_size
branch_method(output, block, recurse)
return
prefix_lines = map(indentation_method, lines)
--
http://mail.python.org/mailman/listinfo/python-list
