This panel summarizes the built-in expression syntax used in External Parameters and many Hamiltonian parameters (including comma‑separated vector parameters like a(3), A(3), etc.).

Expression syntax

• Operators: + - * / ** % and parentheses.
• ^ is accepted as a synonym for **.
• ln(x) is accepted as a synonym for log(x).
• Greek symbols are accepted and normalized: π→pi, θ→theta, φ→phi.
• Examples: To construct skyrmions: θ: 360*atan(exp(3-r))/pi, φ: p.

Symbols / variables

• v — sweep parameter (set v=(0,1) to enable Nv).
• x,y,z — per‑site coordinates provided by the code (typically in Å for real‑space textures).
• r — radial distance; t/theta, p/phi — polar/azimuth angles (degrees) derived from x,y,z when available.
• Constants: pi, e.

Allowed functions

Complex numbers (Hamiltonians)

• Use i for the imaginary unit (also accepts shorthand like 1i, -0.5i).
• Examples: -1i*alpha_R, M*(m1 - 1i*m2).

Comma‑separated vector parameters

If something doesn’t update as expected, open the browser console — expression parsing warnings/errors are reported there.