confused about == vs === in this equality
- To: mathgroup at smc.vnet.net
- Subject: [mg103732] confused about == vs === in this equality
- From: "Nasser Abbasi" <nma at 12000.org>
- Date: Sun, 4 Oct 2009 05:35:38 -0400 (EDT)
- References: <20091003104738.LCJ3I.416659.imail@eastrmwml34>
- Reply-to: "Nasser Abbasi" <nma at 12000.org>
?=== lhs===rhs yields True if the expression lhs is identical to rhs, and yields False otherwise. ?== lhs==rhs returns True if lhs and rhs are identical. But looking at this example: a = ComplexInfinity; If[a == ComplexInfinity, Print["YES"]] Expecting it would print "YES", but it does not. it just returns the whole thing unevaluated? But If[a === ComplexInfinity, Print["YES"]] does return YES. I guess I am a little confused about the "expression" bit in the definition. So, when using the 3"=", it is looking at the _value_ of the expression, but when using the 2"=", it is looking at the expression _as it is_, i.e. without evaluating it? Is this the difference? I've always used the 2"=" for equality, now I have to be more careful which to use. --Nasser __________ Information from ESET NOD32 Antivirus, version of virus signature database 4478 (20091003) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com
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- Re: confused about == vs === in this equality
- From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
- Re: confused about == vs === in this equality