Feel++ Mathematical Keywords Mesh Mesh-related keywords and helper functions. Mathematical Expressions Expression language keywords and elementary functions available in Feel++. Geometry Geometry-related keywords (points, normals, jacobians) available in expressions. Vectors and Matrices Algebraic keywords for vector and matrix creation/manipulation. Operators Operators and differential operators available in the expression language. Multiscale Image Multiscale image handling keywords and utilities. Fitting Data fitting and interpolation keywords (fit, fitDiff).