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Re: What is @@@?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87194] Re: What is @@@?
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Fri, 4 Apr 2008 02:54:51 -0500 (EST)
  • Organization: University of Bergen
  • References: <ft2au1$ph5$1@smc.vnet.net>

Kevin J. McCann wrote:
> I have seen several references to the command @@@ in this newsgroup, but 
> a query of the online Documentation Center just refers me to Apply (@@). 
> What does it do and where can I read about it?
> 

Hi Kevin,

@@@ is "apply at level 1".  f @@@ expr is equivalent to
Apply[f, expr, {1}].  This is under "more information" on the
doc page of Apply[].

It is easy to remember the sytax: each of @, @@, and @@@ act at a deeper 
level:

In[1]:= f@{{1, 2}, {3, 4}}
Out[1]= f[{{1, 2}, {3, 4}}]

In[2]:= f @@ {{1, 2}, {3, 4}}
Out[2]= f[{1, 2}, {3, 4}]

In[3]:= f @@@ {{1, 2}, {3, 4}}
Out[3]= {f[1, 2], f[3, 4]}

But there is no @@@@, it only goes until @@@.

Szabolcs


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