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Re: bug in InputForm (Mathematica 9)?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg132500] Re: bug in InputForm (Mathematica 9)?
  • From: Szabolcs HorvÃt <szhorvat at gmail.com>
  • Date: Wed, 2 Apr 2014 02:36:53 -0400 (EDT)
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note: also sent to comp.soft-sys.math.mathematica

On 2014-3-28, 3:30 , Itai Seggev wrote:
>> Put the following into a notebook cell:
>>
>> InputForm[1]
>> InputForm[2]
>> "test"
>>
>> Evaluate the cell.  Only one of the InputForm commands produces output, and
>> that output comes after "test".
>>
>> I am guessing these behaviors are not intended ...
>>
>> Alan Isaac
>
> An old and well known bug, at least to those of us who work on Mathematica' s
> input/output system. :)  Not as trivial to fix as you might think, because
> doing InputForm[foo] in a notebook lives in this strange world which is half
> command-line terminal and half notebook interface, and so wires can get
> crossed easily.
>

Marginally related to this, I'm curious how all these *Form functions work.

MatrixForm has this slightly confusing property:

In[1]:= a=MatrixForm[{{1,2},{3,4}}]
Out[1]//MatrixForm=
(1	2
  3	4)

In[2]:= Head[a]
Out[2]= MatrixForm

In[3]:= Head[%1]
Out[3]= List

'a' cannot be used as a matrix because it is wrapped in MatrixForm.  But 
MarixForm is stripped before the expression is assgined to Out[1].  It 
is also indicated (using Out[1]//MatrixForm) that the output is shown in 
a special form.

How does MatrixForm achieve this, i.e. that it gets stripped from the 
output and that it's shown in the cell label?  Is there a general, 
user-accessible mechanism for this?  Can I create my own "form-function" 
that behaves like this?

Szabolcs



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