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MathGroup Archive 2007

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Re: IsExact

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80546] Re: IsExact
  • From: Albert <awnl at arcor.net>
  • Date: Sun, 26 Aug 2007 02:55:29 -0400 (EDT)
  • References: <falsi4$gfh$1@smc.vnet.net>

carlos at colorado.edu wrote:
> Let c be a 1D list of scalar coefficients, numeric or symbolic,
> real or complex. No entry is a list. Examples:
> 
> ClearAll[n,x,y,a,a1,a2,b,r];
> c1={1,2*I/5,E^(25*n),3/4+I,Cos[n*x*Pi],y*Sqrt[-5]};
> c2={a/b,r+2/5,a1,,,,,a2};
> c3={1.5,0,Sqrt[3],0,4};
> c4={(r+0.5)/3,3/7,3+Sin[4*x*y]};
> c5={1,2,3,4,5,6}+0.0;
> c6={N[x]};
> 
> I need a function IsExact[c] that returns False if
> at least one entry of c is floating, or if it contains one
> floating number; else True.  For example, tests on
> c1 and c2  should return True; the others False.
> 
my 2 cent:

IsExactQ[x_] := (Length[Cases[x, _Real, Infinity]] == 0)

it doesn't get the last one right, if x is not set to any value. But 
this will not be possible, since c6 doesn't know anything about N having 
been applied to x...

hth,

albert


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