Language Design

• µcad Rules
• The Build Process
  • Parsing Phase
  • Resolving Phase
  • Evaluation Phase
  • Rendering
  • Export Phase

µcad Rules

To stay on course while continuing development of µcad we have expressed some rules that may guide us:

1. µcad is a declarative markup language. This means µcad avoids imperative control flow statements like for, while or goto.
2. Complex generic functionalities (like generating objects or mathematical functionalities) shall be put into builtin libraries instead of implementing them within µcad itself.
3. The standard library shall implement a convenient interface to the builtin library.
4. µcad enforces a strict modular concept to improve code quality.
5. Explicit naming of arguments (within in calls) is encouraged.
6. Explicit writing of units at values is forced.

The Build Process

The µcad interpreter runs programs which generate geometry files. The processing of µcad source code files into output files can be divided into separate phases:

Parsing Phase

In the parsing phase one source file is read into a syntax tree by using the µcad parser. Any errors which occur within the parsing phase are related to file access or syntax.

Resolving Phase

In the resolving phase, the following steps are done:

1. the search paths will be recursively scanned for any external µcad files
2. all symbols (e,g, parts, functions, constants and modules) in the source file will be put into a symbol tree

At the end all dependent files are loaded and syntax definitions are placed in the symbol tree and everything can be found by it's qualified name.

Evaluation Phase

In the evaluation phase, the syntax tree will be processed into a model tree which is a structured representation of the geometry. While this phase the following things will be done:

• expressions will be calculated
• functions will be called
• parts will generate model nodes
• user messages will be output on console

Any errors which occur within the evaluation phase are related to semantic issues.

Rendering

A rendered (like an STL or SVG) renders the model tree into its specific representation, like triangle meshes or polygons.

Export Phase

In the export phase, the renderers representation will be taken to generate 2D or 3D output files (e.g. SVG or STL). While this phase the following things will be done:

• geometric operations will be processed
• geometries will be rendered
• the output files will be written

Any errors which occur within the export phase are related to geometrical processing or file access.