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Path: utzoo!watmath!clyde!cbosgd!cbuxc!cbuxb!cbrma!karl
From: karl@cbrma.UUCP (Karl Kleinpaste)
Newsgroups: net.unix-wizards
Subject: Re: More C-shell weirdness [Another word count problem]
Message-ID: <4366@cbrma.UUCP>
Date: Thu, 3-Apr-86 11:30:33 EST
Article-I.D.: cbrma.4366
Posted: Thu Apr  3 11:30:33 1986
Date-Received: Sat, 5-Apr-86 07:41:34 EST
References: <684@nbires.UUCP>
Distribution: net
Organization: AT&T-BL, RMAS, Columbus
Lines: 35
Keywords: order of substitutions

In article <684@nbires.UUCP> nose@nbires.UUCP (Steve Dunn) writes:
>This:
>set a = ''
>set a = ($a '')
>echo $#a
>Yields 1
>
>But this:
>
>set a = ('' '')
>echo $#a
>Yields 2
>
>This curious behavior has not actually caused me any trouble but I
>am a bit puzzled

It's because of the order in which things are being substituted in the
input line.  That is, what is happening is that
	set a = ($a '')
becomes
	set a = ( '')
when $a's empty value is stuffed into the line.  Then the
interpretation of the remainder gives `a' the single value ''.

As a counterpoint, try
	set a = ''
	set a = ("$a" '')
	echo $#a
which yields 2.  The reason is that you've stipulated extra quotings,
which preserve values for longer than the simple replacement of $a in
the input line with its null value.  The use of double quotes causes
$a to be interpreted within them, subsituting its null string, while
leaving that null string quoted, so that two null strings result.
-- 
Karl Kleinpaste