Component development

Basic structure

• For instrument/comp/particle parameters and variable scope see table Variables and Scopes
• Basic tips for Writing Components
  (includes an exercise and a walkthrough of Slit.comp)

Parameter naming and units

Please consult and adhere to our

• McStas NOMENCLATURE and units of SI and neutron standard units (wavelengths in Å, energy in meV, cross-sections in barns).
• McXtrace NOMENCLATURE and units of SI and X-ray standard units (wavelengths in Å, energy in keV, cross-sections in barns or some cases 1/m).
• Inspire from existing components of similar type and choose similar variable names.

In-component documentation

• Writing a parsable mcdoc component header

Component (unit) testing

• Write an example instrument

Run mctest

• The mctest tool can be used to test a set of McStas/McXtrace instruments

Tips and tools for improving quality of your code

• Keep it simple - complexity means a harder time debugging.
• Choose algorithmic simplicity / readability over performance.
• Document (in language that your colleague also understands) what your code is meant to do. You will even not fully remember yourself in a matter of months!
• Please always be mindful and act on / minimise the number warnings from your c-compiler!
• Run the mccode linter
• If you experience weird crashes it is time for Debugging the c-code

Code (indentation) style

• Please use the utiltity (python-)script McCode/devel/bin/mccode-clangformat to format your new component according to the McCode standard ./devel/bin/mccode-clangformat --file mcstas-comps/contrib/My_new.comp

A tip for a good workflow

• We recommend to use the option to Build your own McStas or McXtrace via conda‐forge directly from your personal fork of McCode.