Determine if a string is collapsible: Difference between revisions

=={{header|sed}}==

Since sed has no native support for arithmetic, line length counting is omitted in this solution for simplicity:

<syntaxhighlight lang="sed">h

s/.*/<<<&>>>/

x

s/\(.\)\1*/\1/g

s/.*/<<<&>>>/

H

s/.*//

G</syntaxhighlight>

Test:

<pre>

printf '%s\n' \

'' \

'"If I were two-faced, would I be wearing this one?" --- Abraham Lincoln ' \

'..1111111111111111111111111111111111111111111111111111111111111117777888' \

"I never give 'em hell, I just tell the truth, and they think it's hell. " \

' --- Harry S Truman ' \

| sed -f collapse.sed

</pre>

{{out}}

<pre>

<<<>>>

<<<>>>

<<<"If I were two-faced, would I be wearing this one?" --- Abraham Lincoln >>>

<<<"If I were two-faced, would I be wearing this one?" - Abraham Lincoln >>>

<<<..1111111111111111111111111111111111111111111111111111111111111117777888>>>

<<<.178>>>

<<<I never give 'em hell, I just tell the truth, and they think it's hell. >>>

<<<I never give 'em hel, I just tel the truth, and they think it's hel. >>>

<<< --- Harry S Truman >>>

<<< - Hary S Truman >>>

</pre>