a conflicting StringReplace
- To: mathgroup at smc.vnet.net
- Subject: [mg56306] a conflicting StringReplace
- From: Hui Fang <fangh73 at xmu.edu.cn>
- Date: Thu, 21 Apr 2005 05:36:35 -0400 (EDT)
- Organization: Xiamen University Photonics Center
- Reply-to: fangh73 at xmu.edu.cn
- Sender: owner-wri-mathgroup at wolfram.com
I was teaching Mathematica in a college. In the class I was showing them
some built-in functions about strings. Since this is not a very
important issue, I didn't spend much time on each function. When I show
them StringReplace, I gave them the following examples:
In[1] StringReplace["abc",{"ab"->"AB"}]
Out[1] ABc
In[2] StringReplace["abc", {"bc"->"BC"}]
Out[2] aBC
No problem on those. Now a student tried the following:
In[3] StringReplace["abc", {"ab"->"AB", "bc"->"BC"}]
Out[3] ABc
Now he asked me why only "ab" is replaced. I said this is because there
is a conflict because both "ab" and "bc" contains "b". So Mathematica
will choose the first replacement. I also told him if he changes the
order, he will get aBC. Now:
In[4] StringReplace["abc", {"bc"->"BC","ab"->"AB"}]
Out[4] ABc
This is the part I don't understand. Does Mathematica treat those rules
in their canonical order (since "ab" is before "bc" in canonical
order.), or in their written order?
Thanks a lot!
Hui Fang
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