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The difference between Needs[ ] & Get[ ]

• To: mathgroup at smc.vnet.net
• Subject: [mg40149] The difference between Needs[ ] & Get[ ]
• From: "neuron" <b90401114 at ntu.edu.tw>
• Date: Sat, 22 Mar 2003 05:10:39 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Hello MathGroup gurus,
I am new to Mathematica and now reading "Programming In Mathematica."
I am a little  confused with Needs[ ] & Get[ ].
I kow that  Needs[ ] checks $Packages whether the package is present or 
not and I usually use Needs[ ] to load a package.
On the xiv page of "ProgrammingInMathematica" it says "Even better is 
Needs["ProgrammingInmathematica`Package`"]........"
but on page 13,
when I input
Needs["ProgrammingInMathematica`ComplexMap1`"]
instead of
<<ProgrammingInMathematica`ComplexMap1`
an error occurs:
Needs::nocont: Context ProgrammingInMathematica`ComplexMap1` was not 
created when Needs was evaluated.

I don't know why, for the Help says "Needs["context`"] calls 
Get["context`"]. By convention, the file loaded in this way is the one 
which contains a package that defines context`. "

I execute Mathematica 4.1 on Windows98

 Thanks for any advice.