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Re: ways to save the output from a notebook

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93431] Re: [mg93408] ways to save the output from a notebook
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 7 Nov 2008 06:02:37 -0500 (EST)
  • Reply-to: hanlonr at cox.net

Immediate evaluation:

Clear[F];

F[x1_, x2_] = Module[{Yeni, Eski}, Yeni = x1^2;
  Eski = x2^3]

x2^3

?F

Global`F

F[x1_,x2_]=x2^3


Table[F[x1, x2], {x1, 3}, {x2, 3}];

?F

Global`F

F[x1_,x2_]=x2^3


The definition of F has not been changed by use.



Delayed evaluation :

Clear[F];

F[x1_, x2_] := Module[{Yeni, Eski}, Yeni = x1^2;
  Eski = x2^3]

?F

Global`F

F[x1_,x2_]:=Module[{Yeni,Eski},Yeni=x1^2;Eski=x2^3]


Table[F[x1, x2], {x1, 3}, {x2, 3}];

?F

Global`F

F[x1_,x2_]:=Module[{Yeni,Eski},Yeni=x1^2;Eski=x2^3]


Again, the definition of F has not been changed by use.



Delayed evaluation with embedded immediate evaluation:

Clear[F];

F[x1_, x2_] := F[x1, x2] = Module[{Yeni, Eski}, Yeni = x1^2;
    Eski = x2^3];

Note that the patterns only appear on the far LHS

?F

Global`F

F[x1_,x2_]:=F[x1,x2]=Module[{Yeni,Eski},Yeni=x1^2;Eski=x2^3]


Table[F[x1, x2], {x1, 3}, {x2, 3}];

?F

Global`F

F[1,1]=1
 
F[1,2]=8
 
F[1,3]=27
 
F[2,1]=1
 
F[2,2]=8
 
F[2,3]=27
 
F[3,1]=1
 
F[3,2]=8
 
F[3,3]=27
 
F[x1_,x2_]:=F[x1,x2]=Module[{Yeni,Eski},Yeni=x1^2;Eski=x2^3]


The definition of F remembers the results of each call. This is particularly useful to speed up multiple calls to recursive defintions. See

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


Bob Hanlon

---- Tugrul Temel <temelt at xs4all.nl> wrote: 

=============
Dear All,

Suppose that I have:

F[x1_,x2_]:=F[x1_,x2_]=
   Module[
   {Yeni, Eski},
    Yeni=x1^2 ;
    Eski=x2^3
         ]

What role does F[x1_,x2_]:=F[x1_,x2_] have? What does it do?

Regards,
Tugrul
 


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