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MathGroup Archive 1999

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Re: Re: Re: equaltity of lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19175] Re: [mg19147] Re: [mg19092] Re: [mg19036] equaltity of lists
  • From: Maarten.vanderBurgt at icos.be
  • Date: Tue, 10 Aug 1999 02:52:40 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Kevin,

Maybe I do not understand your remark completely. But when I do this on my
PC  (Mathematica 4.0) I get

In[1] := Signature[{a, b, c, d}]
Out[1] = 1

In[2] := Signature[{a, b, d, c}]
Out[2] = -1

Which is completely in line with the definition of Signature.
Canonical order has nothing to do with sameness or equality.

Maarten





"Kevin J. McCann" <kevinmccann at Home.com> on 06-08-99 05:58:49 AM


Subject: [mg19175]  [mg19147] Re: [mg19092] Re: [mg19036] equaltity of lists




Maarten


Agree with you, but then why do you get

Signature[{a,b,c,d}]
True

Signature[{a,b,d,c}]
False

By the same logic this should not return an answer.

Kevin


----- Original Message -----
From: <Maarten.vanderBurgt at icos.be>
To: mathgroup at smc.vnet.net
Subject: [mg19175] [mg19147] [mg19092] Re: [mg19036] equaltity of lists


> Drago,
>
> You should use
>
> {a, b} === {b, a}
>
> when you want False as a result.
>
> The following I copied from the Mathematica help files. This explains the
> difference between '===' and '=='.
>
> SameQ
> -----
> lhs === rhs yields True if the expression lhs is identical to rhs, and
> yields False otherwise.
>
> SameQ requires exact correspondence between expressions, except that it
> considers Real numbers equal if their difference is less than the
> uncertainty of either of them.
>
> 2 === 2. gives False.
>
> e1 === e2 === e3 gives True if all the ei are identical.
>
>
> Equal
> -----
> lhs == rhs returns True if lhs and rhs are identical.
>
> lhs == rhs is used to represent a symbolic equation, to be manipulated
> using functions like Solve.
>
> lhs == rhs returns True if lhs and rhs are identical expressions.
>
> lhs == rhs returns False if lhs and rhs are determined to be unequal by
> comparisons between numbers or other raw data, such as strings.
>
> Approximate numbers are considered equal if they differ in at most their
> last eight binary digits (roughly their last two decimal digits).
>
> 2 == 2. gives True.
>
> e1 == e2 == e3 gives True if all the ei are equal.
>
>
>
>
> Maarten
>
>
>
>
>
>
> "Drago Ganic" <drago.ganic at in2.hr> on 03-08-99 07:45:05 PM
>
>
> Subject: [mg19175] [mg19147] [mg19092]  [mg19036] equaltity of lists
>
>
>
>
> Hi !!
>
> Why don't I get an answer (False) when I ask Mathematica
>
>     {a,b}=={b,a}
>
> like the one I get with
>
>     {1,2}=={2,1}
>     False
>
> Greetings from Croatia,
> Drago Ganic
>
>
>
>
>
>
>
>








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