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From: guerom00 on 29 Mar 2010 08:20
Hello all,

Just a quick question : what are the priority between all those
operators ? I mean :
- what is f@x//g ? Is it f[g[x]] or g[f[x]]
- what is f@@{a,b}[[2]] ? Is it f[b] or (f[a,b])[[2]]

You see what I mean... What are the rules for the priority of all
those operators ?

TIA :)

From: Murray Eisenberg on 30 Mar 2010 06:00
This is always a thorny issue when you use "abbreviations" such as
prefix form, suffix form, etc. In the Documentation Center, look at the
page:

tutorial/OperatorInputForms

There you'll see two long tables listing all the input forms in order of
decreasing precedence.

On 3/29/2010 8:20 AM, guerom00 wrote:
>
> Just a quick question : what are the priority between all those
> operators ? I mean :
> - what is f@x//g ? Is it f[g[x]] or g[f[x]]
> - what is f@@{a,b}[[2]] ? Is it f[b] or (f[a,b])[[2]]
>
> You see what I mean... What are the rules for the priority of all
> those operators ?

--
Murray Eisenberg murray(a)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

From: DrMajorBob on 30 Mar 2010 05:59
Don't memorize rules. When in doubt, highlight an operator and double or
triple click to see what expansion of the selection occurs.

Bobby

On Mon, 29 Mar 2010 07:20:10 -0500, guerom00 <guerom00(a)gmail.com> wrote:

> Hello all,
>
> Just a quick question : what are the priority between all those
> operators ? I mean :
> - what is f@x//g ? Is it f[g[x]] or g[f[x]]
> - what is f@@{a,b}[[2]] ? Is it f[b] or (f[a,b])[[2]]
>
> You see what I mean... What are the rules for the priority of all
> those operators ?
>
> TIA :)
>


--
DrMajorBob(a)yahoo.com

From: Bob Hanlon on 30 Mar 2010 06:00

To find out, evaluate the expressions.

f@x // g

g[f[x]]

f @@ {a, b}[[2]]

b

For the precedence of operators see :

http://reference.wolfram.com/mathematica/tutorial/OperatorInputForms.html

@ has higher precedence than //

[[ ]] has higher precedence than @@
However, this makes no difference for the last example above

(f @@ {a, b})[[2]] == f @@ ({a, b}[[2]])

True

And if you want to make sure, use parentheses to force the evaluation order.


Bob Hanlon

---- guerom00 <guerom00(a)gmail.com> wrote:

=============
Hello all,

Just a quick question : what are the priority between all those
operators ? I mean :
- what is f@x//g ? Is it f[g[x]] or g[f[x]]
- what is f@@{a,b}[[2]] ? Is it f[b] or (f[a,b])[[2]]

You see what I mean... What are the rules for the priority of all
those operators ?

TIA :)



From: Bill Rowe on 30 Mar 2010 06:01
On 3/29/10 at 7:20 AM, guerom00(a)gmail.com (guerom00) wrote:

>Just a quick question : what are the priority between all those
>operators ? I mean : - what is f@x//g ? Is it f[g[x]] or g[f[x]] -
>what is f@@{a,b}[[2]] ? Is it f[b] or (f[a,b])[[2]]

>You see what I mean... What are the rules for the priority of all
>those operators ?

The easy thing to do is simply execute an example. That is:

In[1]:= f@x // g

Out[1]= g[f[x]]

In[2]:= f @@ {a, b}[[2]] // Trace

Out[2]= {{{a,b}[[2]],b},f@@b,b}

Or look at the documentation. Specifically,

tutorial/OperatorInputForms


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