Re: How do I eliminate premultipliers of "1." ?
- To: mathgroup at smc.vnet.net
- Subject: [mg31162] Re: How do I eliminate premultipliers of "1." ?
- From: "Alan Mason" <swt at austin.rr.com>
- Date: Sun, 14 Oct 2001 04:11:56 -0400 (EDT)
- References: <9q8oeb$co$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hello Brett. You can get rid of them by applying a rule. In[9]:= expr = 1.0 a Out[9]= 1. a In[10]:= expr2 = expr /. 1.0 u_:> u Out[10]= a .. I agree with you, though. Mathematica 4.1 even claims that 1.0 == 1 is True. In[5]:= 1.0 \[Equal] 1 Out[5]= True I consider this an outright error. 1.0 means a floating-point approximation to 1, whereas 1 is exactly 1 The correct way to treat 1.0/1.0 is somewhat ambiguous. Does 1.0 stand for the same approximation at each appearance? If so, the ratio should be 1; otherwise, it should be 1.0. Alan "Brett Patterson" <bap at roe.ac.uk> wrote in message news:9q8oeb$co$1 at smc.vnet.net... > Consider the following: > > In[1] := 1 a / 1 > Out[1] := a > > In[2] := 1.0 a / 1.0 > Out[2] := 1. a > > Now consider these identities: > > In[3] := (1 / 1) == 1 > Out[3] := True > > In[4] := (1.0 / 1.0) == 1.0 > Out[4] := True > > In[5] := (1 / 1) == 1.0 > Out[5] := True > > In[6] := (1.0 / 1.0) == 1 > Out[6] := True > > Given that it is clear mathematically that I want the > answer to In[2] to evaluate to just "a", and given that > Mathematica is clearly recognizing that 1.0 / 1.0 is the > same as 1 / 1, can someone please tell me why Out[2] contains > the premultiplier "1." and how to eliminate it in expressions > that might contain this superfluous unit multiplier in various places. > > Thanks! > > Brett Patterson > > UK Astronomy Technology Centre > The Royal Observatory > Blackford Hill > Edinburgh EH9 3HJ > Scotland >
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