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Re: Re: Programming style: postfix/prefix vs. functional

• To: mathgroup at smc.vnet.net
• Subject: [mg70671] Re: [mg70633] Re: [mg70587] Programming style: postfix/prefix vs. functional
• From: "Chris Chiasson" <chris at chiasson.name>
• Date: Sun, 22 Oct 2006 01:20:41 -0400 (EDT)
• References: <200610200921.FAA11092@smc.vnet.net> <200610210914.FAA29189@smc.vnet.net> <453A4431.5040102@math.umass.edu>

You just made me realize I typed my question incorrectly. @ isn't in
the documentation for Operate as I originally said. It's in the
documentation for Composition.

Seeing it written out like

Composition[f,g][expr]

and

f@g[expr]

does help drive the point home

I guess one question I have about that is:

Why aren't these two expressions identical

In[1]:=
HoldComplete[f@g[a]]//FullForm
HoldComplete[Composition[f,g][a]]//FullForm

Out[1]//FullForm=
HoldComplete[f[g[a]]]

Out[2]//FullForm=
HoldComplete[Composition[f,g][a]]


On 10/21/06, Murray Eisenberg <murray at math.umass.edu> wrote:
> @ is an abbreviation for Composition:
>
>    Composition[f, g][expr]
> f[g[expr]]
>
>    f@g[expr]
> f[g[expr]]
>
> But this one is a bit difficult to discover from the documentation.  If
> you know the term "Composition", then of course you can do the reverse
> look-up in the Help Browser.
>
> Unfortunately, if you try the Help Browser directly for "@", even using
> the Master Index tab, you won't find it!
>
> Moreover, if you try the default Built-in Functions tab you search for
> @, you'll be taken to the entry for Apply (@@).
>
> So this is definitely a gap in the documentation indexing.
>
>
> Chris Chiasson wrote:
> > One thing I have wondered is, what function corresponds to the short
> > hand "@". I know @ appears in Operate. Also, the ? can sometimes tell
> > what function an operator represents (try ?/@ ) , but ?@ only gives
> > System`$ (the symbol $ in the context System).
> >
> >
> > On 10/20/06, Will Robertson <wspr81 at gmail.com> wrote:
> >> Hello,
> >>
> >> As a newcomer to Mathematica, I'm a little unsure on what "good style"
> >> would be in this programming language. I notice that several functions
> >> have prefix and postfix notations such as //. for ReplaceRepeated, /@
> >> for Map, and so on.
> >>
> >> Clearly using these forms makes the code more compact, but sacrifices
> >> some level of readability. Are there guidelines or suggestions that
> >> have built up over the years of whether these are "good" or "bad" to
> >> use?
> >>
> >> If it's simply personal preference, what do you like to use?
> >> --
> >> Many thanks,
> >> Will Robertson
> >>
> >>
> >
> >
>
> --
> Murray Eisenberg                     murray at math.umass.edu
> Mathematics & Statistics Dept.
> Lederle Graduate Research Tower      phone 413 549-1020 (H)
> University of Massachusetts                413 545-2859 (W)
> 710 North Pleasant Street            fax   413 545-1801
> Amherst, MA 01003-9305
>


-- 
http://chris.chiasson.name/

• References:
  • Programming style: postfix/prefix vs. functional
    • From: "Will Robertson" <wspr81@gmail.com>
  • Re: Programming style: postfix/prefix vs. functional
    • From: "Chris Chiasson" <chris@chiasson.name>