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## 11.1 Names, Abbreviations, and File Structure

Each package has a name and an abbreviation. For a package of the complex draw functions from Chapter ugIntProg , we choose the name DrawComplex and abbreviation:constructor abbreviation DRAWCX.An abbreviation can be any string of constructor:abbreviation between two and seven capital letters and digits, beginning with a letter. See ugTypesWritingAbbr for more information. To be sure that you have not chosen a name or abbreviation already used by the system, issue the system command )show for both the name and the abbreviation. show

Once you have named the package and its abbreviation, you can choose any new filename you like with extension `` .spad'' to hold the definition of your package. We choose the name drawpak.spad. If your application involves more than one package, you can put them all in the same file. Axiom assumes no relationship between the name of a library file, and the name or abbreviation of a package.

Near the top of the `` .spad'' file, list all the abbreviations for the packages using )abbrev, each command beginning in column one. Macros giving names to Axiom expressions can also be placed near the top of the file. The macros are only usable from their point of definition until the end of the file.

Consider the definition of DrawComplex in Figure fig-pak-cdraw . After the macro macro definition

S ==> Segment DoubleFloat

the name S can be used in the file as a shorthand for Segment DoubleFloat.The interpreter also allows macro for macro definitions. The abbreviation command for the package

)abbrev package DRAWCX DrawComplex

is given after the macros (although it could precede them).

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