Here is a list of all files with brief descriptions:

[detail level 1234]

docs
patterns
user_guides
include
janus
core
Diagnostics.hpp	Structural observability and identifiability analysis
Function.hpp	Symbolic function wrapper around CasADi with Eigen-native IO
JanusConcepts.hpp	C++20 concepts constraining valid Janus scalar types
JanusError.hpp	Custom exception hierarchy for Janus framework
JanusIO.hpp	IO Utilities and Traits for Janus
JanusTypes.hpp	Core type aliases for numeric and symbolic Eigen/CasADi interop
Sparsity.hpp	Sparsity pattern analysis, graph coloring, and sparse derivative evaluators
StructuralTransforms.hpp	Alias elimination, BLT decomposition, and structural analysis passes
math
Arithmetic.hpp	Scalar and element-wise arithmetic functions (abs, sqrt, pow, exp, log, etc.)
AutoDiff.hpp	Symbolic automatic differentiation (Jacobian, gradient, Hessian, sensitivity analysis)
Calculus.hpp	Numerical differentiation and integration (gradient, trapz, cumtrapz, diff)
FiniteDifference.hpp	Finite difference weights, derivative approximations, and integration defects
Integrate.hpp	ODE integration for Janus framework
IntegrateDiscrete.hpp	Discrete integration and squared-curvature computation from sampled data
IntegratorStep.hpp	Single-step explicit ODE integrators for Janus framework
Interpolate.hpp	N-dimensional interpolation (linear, Hermite, B-spline, nearest)
JanusMath.hpp	Master header for Janus Math library Includes all math sub-modules
Linalg.hpp	Linear algebra operations (solve, inverse, determinant, eigendecomposition, norms)
Logic.hpp	Conditional selection, comparison, and logical operations
OrthogonalPolynomials.hpp	Orthogonal polynomial evaluation, spectral nodes, weights, and differentiation matrices
PolynomialChaos.hpp	Polynomial chaos expansion (PCE) basis, projection, and regression
Quadrature.hpp	Stochastic quadrature rules (Gauss, Clenshaw-Curtis, Smolyak sparse grids)
Quaternion.hpp	Quaternion algebra, rotation, and SLERP interpolation
RootFinding.hpp	Nonlinear root finding and implicit function solvers
Rotations.hpp	2D and 3D rotation matrices and Euler angle conversions
ScatteredInterpolator.hpp	RBF-based interpolation for unstructured scattered data
Spacing.hpp	Point distribution generators (linspace, cosine, sine, log, geometric)
SurrogateModel.hpp	Smooth surrogate functions (softmax, softmin, softplus, sigmoid, blend, KS aggregation)
Trig.hpp	Trigonometric and inverse trigonometric functions
optimization
BirkhoffPseudospectral.hpp	Birkhoff pseudospectral transcription for trajectory optimization
Collocation.hpp	Direct Collocation for Trajectory Optimization
MultiShooting.hpp	Multiple Shooting for Trajectory Optimization
Opti.hpp	High-level nonlinear programming interface
OptiOptions.hpp	Solver selection and configuration for Opti
OptiSol.hpp	Solution wrapper for extracting optimized values
OptiSweep.hpp	Parametric sweep results for optimization problems
Pseudospectral.hpp	Pseudospectral transcription for trajectory optimization
Scaling.hpp	Scaling diagnostics and metadata for optimization problems
TranscriptionBase.hpp	Shared CRTP base for trajectory transcription methods
utils
JsonUtils.hpp	Simple JSON read/write utilities for flat string-to-vector maps
janus.hpp	Umbrella header that includes the entire Janus public API
using.hpp	Convenience header bringing common Janus symbols into scope