Hint to Part 8 Exercise

	Hint to Part 8 Exercise

	Using a global command can cut the length of the command
	sequence roughly in half. The correct way to use it depends on
	something I did not explicitly say about global commands, but
	which you should be able to guess from what I did say.

	Answer to Part 8 Exercise

	A fairly simple way to handle both writing the tab-revised
	version of your file and keeping the original version in the
	editor buffer is this sequence:

	:.g/^/%s/\({\)^I^I/\1{/g\|%s/^\({\)^I/\1 /\|%s/{/^I/g\|w
	u

	The first line is pretty straightforward, excepting the initial
	global command. Otherwise it just replaces every pair of tabs at
	the start of a line with the dummy character "{", then changes
	any remaining solitary tab in the initial whitespace with four
	space characters, changes every dummy "{" to a single tab, and
	finally writes the file.

	That initial global command seems silly, I know. It scans over
	just the current line, it marks that line without fail because
	every line has a starting point, and so it ends up running the
	remaining commands on the line for sure and exactly once. This is
	just what the command line would do without that initial global.
	So why is it there?

	The answer is in that second line. When you run an undo after a
	global command, you don't just undo the last command the global
	ran; you undo every buffer change done by every command the
	global ran. (Note that the u is not preceded by a colon (":");
	it is a screen-mode command.) So as soon as the write is
	finished, the undo puts the entire buffer back as it was.

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