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MathGroup Archive 2005

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Re: Position different in 5.0 and 5.1?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56108] Re: Position different in 5.0 and 5.1?
  • From: Peter Pein <petsie at arcor.de>
  • Date: Fri, 15 Apr 2005 04:48:23 -0400 (EDT)
  • References: <d3lraa$s6b$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

J R Gog wrote:
> I've recently upgraded from 5.1 from 5.0 and have found that some of my old 
> notebooks don't seem to work. I think I have the essence of what I'm utterly 
> confussed about in this example:
> Position[{"asd", "dsa"}, x_ /; (StringTake[x, 1] == "a")]
> 
> What I want is the position of list entries which have first character "a". 
> In 5.0, this line works. In 5.1, I get an error that StringTake is being fed 
> a string.
> 
> I can't find any documentation that explains what has changed to have this 
> effect. I'm sure I've missed something obvious, but if anyone can explain to 
> me what has changed, it would be very helpful indeed. I know I can do 
> everything some other way, but I need to know exactly what old stuff I need 
> to change!
> 
> 
> 
> Thanks
> 
> 
> 
> Julia Gog
> 
> 
x_ shall match strings only:

Position[{"asd", "dsa"}, x_String /; (StringTake[x, 1] == "a")]

or avoid evaluation of StringTake[List,1] by typing

Position[{"asd", "dsa"}, x_ /; (StringTake[x, 1] == "a"), Heads -> False]

-- 
Peter Pein
Berlin



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