Design

The API that Doodle presents to the user should be compositional and easy to reason about. There are fundamental ideas in functional programming. Internally, the implementation may be a stateful program, as the majority of graphics library are implemented in a stateful way.

Conveniences

We provide convenience operations for common operations. For example, we can just draw a Picture without providing a Canvas or Frame, or having to deal with IO. The most convenient operation is usually presented as the default. So we expect people will want to use draw more than drawWithFrame or drawToIO, and hence it has the shortest name and is introduced first in documentation.

Conveniences should be implemented as syntax. Try to keep algebras to the minimal set of most basic operations. Note that the current system doesn't follow this advice very closely. Until we figured how to make the current architecture it was expected that people would frequently interact directly with algebras, so they tend to contain more methods than is strictly necessary.

The default operations, provided as syntax, generally do not expose IO. Altneratives that do expose IO are suffixed toIO. So, for example, draw is the default operation to render a Picture and does not expose an IO. The syntax that does is called drawToIO.

There are a couple of naming conventions in use:

• operations that require more parameters than the default are suffixed with withA, where A is the type. E.g. drawWithFrame.
• operations that produces a different output type are suffixed with toA, where A is the type. E.g. drawToIO.
• the above can be combined, as in drawWithFrameToIO.

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