Groups > comp.soft-sys.math.mathematica > #2955

Question about function construction

From	ZiYuan Lin <ziyuang@gmail.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Question about function construction
Date	2011-06-05 11:04 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<isfnrv$btm$1@smc.vnet.net> (permalink)

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Hi, there.
  I want to construct a function serving as a hash table. This is how I make it:

  ConstructHashtable[] := 
   Module[{pairs = {{"key1", "value1"}, {"key2", "value2"}, {"key3", 
        "value3"}, {"key4", "value4"}}}, Clear[Hashtable]; 
    Hashtable[key_?StringQ] := (Hashtable[#[[1]]] = #[[2]]) & /@ pairs;]

And then I run the code above together with a test:

  ConstructHashtable[]; Hashtable["key1"]

Yet it returns all values:

  {"value1", "value2", "value3", "value4"}

But if I run it again:

  Hashtable["key1"]

It will get normal:

  "value1"

What is the reason for this? Thank you~

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Question about function construction ZiYuan Lin <ziyuang@gmail.com> - 2011-06-05 11:04 +0000
  Re: Question about function construction Albert Retey <awnl@gmx-topmail.de> - 2011-06-06 10:23 +0000

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