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11.2.8 Packages and Libraries (Zusatzpakete und Bibliotheken)
A Maple "package" is a collection of related functions. An example of a package is linalg, the Maple
linear algebra package. To use a package, you initially read it into memory using the with command:
> with(linalg):
Warning: new definition for norm
Warning: new definition for trace
It will also give a bracketed list of functions. When Maple loads a package, it checks to see whether
any of the new function names will replace an existing function. If so, it gives you a warning. For
instance, since linalg has a function to compute the trace of a matrix that is called "trace", which is the
same name as the debugging command "trace", a warning was generated. The new function is
available for use, but the previous function of the same name is no longer accessible.
There is a way to avoid this problem if you want access to both functions. The technique will allow you
to use a single function of a package without loading the entire package into memory. To specify the
function, you use the "long form": libname[funcname](...) where funcname is the function you wish to
use, libname is the package it is contained in, and (...) is the argument list.
A Maple "library" is a collection of packages. The standard Maple library consists of some internallydefined
functions, but most of them reside externally on the file system. When you use the readlib
command, Maple reads in the definition for the specified function in much the same way that with
works for packages. readlib is particularly useful in situations where you have redefined a standard
library function.
For example, when the linalg package was loaded in, the standard trace function became
unavailable. To get it back, use:
> readlib('trace');
proc(fname) ... end
11.2.9 Restoring and Saving Sessions (Sichern und Wiederherstellen)
During the course of a Maple session, you may have entered in a number of useful expressions and
routines that you would like to re-use in future. To avoid retyping them the next time you use Maple,
you can save that work in a file by using the save command.
For example, the following command saves everything you created during the session in a file named
"filename.m":
> save "filename.m";
or:
> save a,b,c,"filename.m"
if you only want to save variables a, b, and c.
When you specify a filename with the extension ".m", Maple saves your work in "Maple internal
format". This format can be read in more quickly by Maple when you restore your work later on, but is
not human-readable. You restore the information with the command:
> read "filename.m";
To save information in a human-readable format (Maple language format), you can type:
> save a,b,c,"filename"
This saves the specified items as a series of assignment statements. To save the entire worksheet,
select File, followed by Save As. For more information on formats, consult Maple's online help.
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