Sage Developer's Guide - Mirrors

Sage Developer’s Guide, Release 6.1.14.2.1 DesignIf you are planning to develop some new code for Sage, design is important. So think about what your program will doand how that fits into the structure of Sage. In particular, much of Sage is implemented in the object-oriented languagePython, and there is a hierarchy of classes that organize code and functionality. For example, if you implement elementsof a ring, your class should derive from sage.structure.element.RingElement, rather than startingfrom scratch. Try to figure out how your code should fit in with other Sage code, and design it accordingly.4.2.2 Special Sage FunctionsFunctions with leading and trailing double underscores __XXX__ are all predefined by Python. Functions with leadingand trailing single underscores _XXX_ are defined for Sage. Functions with a single leading underscore are meant tobe semi-private, and those with a double leading underscore are considered really private. Users can create functionswith leading and trailing underscores.Just as Python has many standard special methods for objects, Sage also has special methods. They are typically ofthe form _XXX_. In a few cases, the trailing underscore is not included, but this will eventually be changed so that thetrailing underscore is always included. This section describes these special methods.All objects in Sage should derive from the Cython extension class SageObject:from sage.ext.sage_object import SageObjectclass MyClass(SageObject,...):...or from some other already existing Sage class:from sage.rings.ring import Algebraclass MyFavoriteAlgebra(Algebra):...You should implement the _latex_ and _repr_ method for every object. The other methods depend on the natureof the object.LaTeX RepresentationEvery object x in Sage should support the command latex(x), so that any Sage object can be easily and accuratelydisplayed via LaTeX. Here is how to make a class (and therefore its instances) support the command latex.1. Define a method _latex_(self) that returns a LaTeX representation of your object. It should be somethingthat can be typeset correctly within math mode. Do not include opening and closing $’s.2. Often objects are built up out of other Sage objects, and these components should be typeset using the latexfunction. For example, if c is a coefficient of your object, and you want to typeset c using LaTeX, uselatex(c) instead of c._latex_(), since c might not have a _latex_ method, and latex(c) knowshow to deal with this.3. Do not forget to include a docstring and an example that illustrates LaTeX generation for your object.4. You can use any macros included in amsmath, amssymb, or amsfonts, or the ones defined inSAGE_ROOT/doc/commontex/macros.tex.An example template for a _latex_ method follows:4.2. Coding in Python for Sage 33