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MathGroup Archive 1996

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Typing, Declare and Mma3.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5002] Typing, Declare and Mma3.0
  • From: jeremy_gorman at smtp.svl.trw.com (Jeremy Gorman)
  • Date: Sat, 19 Oct 1996 02:25:48 -0400
  • Organization: TRW ASG Sunnyvale (formerly ESL)
  • Sender: owner-wri-mathgroup at wolfram.com

With Mma 2.2.2 I find:

In[1]:=
Re[Conj[Re[a]]]
Out[1]=
Re[Conj[Re[a]]]

Type checking is either insufficiently stringent or fails
to distribute properly over the Conj[] function.
I tried using Declare.m from Mathsource, to resolve this,
but still I get:

In[129]:=
Declare[a,Real]
In[130]:=
Re[Conj[a]]
Out[130]=
Re[Conj[a]]

Does Mma 3.0 resolve this for me? If not, is there
some newer Declare.m that will? Can someone suggest how to
extend Declare.m to take care of this for me -- here's what
appears to be the salient part of Declare.m:

Unprotect[RealQ]
RealQ[x_ + y_]:= RealQ[x] && RealQ[y]
RealQ[x_ y_]:= RealQ[x] && RealQ[y]
RealQ[_Real] = True
RealQ[_Integer] = True
RealQ[_Rational] = True
RealQ[_Complex] = False
RealQ[Re[_]] = True
RealQ[Im[_]] = True
RealQ[Arg[_]] = True
RealQ[Abs[_]] = True
RealQ[_?NonNegative ^ _?RealQ] = True
RealQ[_?Negative ^ x_]:= False /; !IntegerQ[x]
RealQ[_?RealQ ^ _?IntegerQ] = True
RealQ[_] = Uncertain
Protect[RealQ]

Unprotect[Re,Im]
Re[x_?RealQ] = x
Im[_?RealQ] = 0
Protect[Re,Im]

Thanks in advance,
Jeremy

/*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/
Jeremy Gorman                                  "Just a Comment"
Most of my opinions are my own (especially if expressed here) !
/*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/ /*\ \*/


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