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Concepts
This section of the documentation covers the use of Objects, Libraries and References, Notations, Styles and Types and how each is created, edited and used in the Sym application.
Styles
Each notation refers to a stylesheet. Stylesheets define Styles. Styles are used in two places. First, they can be used to style text. Second, they can be used to style parts of an expression in a rendering. You can create new style and new stylesheets.
Creating Styles
Styles are defined in Stylesheets. Stylesheets are functions that return the style settings for a given class name. In this topic, we will cover adding new styles to an existing stylesheet. Creating new stylesheets is covered separately.

Concepts
This section of the documentation covers the use of Objects, Libraries and References, Notations, Styles and Types and how each is created, edited and used in the Sym application.
- Objects
  An object is the basic building block of all of the symbolic content contained in a document - every term in every symbolic expression in Sym is an instance of an object. Many of the objects used in Sym have an object definition that specifies how the object looks and behaves, but it's also possible to create objects that don't have object definitions. All objects are identified by their name and object names are always defined in a specific namespace. All object definitions contain a type definition. Optionally, objects can also contain Properties, Clauses, Renderings, and a Description.
- Library Locations and References
  Locations are used to manage groups of libraries and documents. The purpose of locations is to make documents portable from one machine to another. To do that, locations can be online as well as on your local machine. If a document references online libraries, the required libraries will be downloaded automatically when the document is opened.
- Notations and Rendering
  The purpose of notations is to make it possible to easily change the way expressions are displayed. Notations are assigned to Document Modules, Unit Test Modules and Object Modules. The notation assigned determines which renderings are selected for each expression in the module.
- Styles
  Each notation refers to a stylesheet. Stylesheets define Styles. Styles are used in two places. First, they can be used to style text. Second, they can be used to style parts of an expression in a rendering. You can create new style and new stylesheets.
  - Creating Styles
    Styles are defined in Stylesheets. Stylesheets are functions that return the style settings for a given class name. In this topic, we will cover adding new styles to an existing stylesheet. Creating new stylesheets is covered separately.
  - Creating Stylesheets
    Stylesheets determine the fonts and sizes that are used when objects are displayed. They are designed somewhat like cascading style sheets. Creating a new stylesheet just involves creating a new object definition for the new stylesheet.
  - Style Functions
    Part of the process of generating a rendering expression for any expression is getting and applying the styles for the expression.
- Types
  Every term in every expression in a Sym document has a type assigned to it. Every object definition has a type definition as one of its components. Since type definitions can include things like type variables, Sym uses a type inferencing process to determine the explicit types assigned to each term in every expression.

Creating Styles

Styles are defined in Stylesheets. Stylesheets are functions that return the style settings for a given class name. In this topic, we will cover adding new styles to an existing stylesheet. Creating new stylesheets is covered separately.

To add a new style to an existing stylesheet, we just need to create an extension to the stylesheet function and add clauses to it that define the new styles. See Extending Object Definitions for information about extending functions.

In this example, we will add a new class name and extend the Standard stylesheet to include a definition for the new style. The steps are:

Create a new Object Module in either the current document or in a library.
In that module, create the StyleSheets namespace and create an object definition for the new class. In this example, we will use MyAddedClass. The MyAddedClass object should be typed as ClassName.
Create an extension for the standard stylesheet function. This function is called StandardStyleSheet. The type for this object needs to be ClassName → Style.
Add a clause for MyAddedClass to the extension of StandardStyleSheet. At this point your new Object Module should look something like:

The new style will only be available in the current document if the new Object Module is in the current document. If the new module is in a library, the new style will be available in any document that references the library.