Migrating to v0.4

v0.4.0 has two breaking changes. Both produce compile-time or runtime errors, so your test suite will catch them.

1. Series() Wrapper

Multi-series input now requires the Series(...) wrapper. Bare Matrix and Vector{Vector} dispatch has been removed to avoid ambiguity with the new custom value type support.

All input forms are supported:

Series(y1, y2, y3)          # varargs
Series([y1, y2])            # vector of vectors
Series(hcat(y1, y2))        # matrix (columns = series)

2. PeriodicBC() Strict Endpoint Check

The default :inclusive mode now requires y[1] == y[end] (exact equality) instead of isapprox. This catches silent data errors from floating-point arithmetic:

t = range(0, 2π, 101)
y = sin.(t)
# sin(2π) ≈ -2.4e-16, NOT exactly 0.0

cubic_interp(t, y; bc=PeriodicBC())
# ERROR: y[1] != y[end] for inclusive PeriodicBC

Fix by explicitly ensuring the endpoint matches:

y[end] = y[1]   # force exact equality
cubic_interp(t, y; bc=PeriodicBC())  # works

Alternatively, use :exclusive mode if your data does not include the repeated endpoint:

t = range(0, 2π, 101)[1:end-1]   # exclude last point
y = sin.(t)
cubic_interp(t, y; bc=PeriodicBC(:exclusive))