(breaking): remove legacy Symbol extrapolation API

.github/workflows/Benchmark.yml

@@ -41,9 +41,6 @@ jobs:
       - name: Cache Julia artifacts
         uses: julia-actions/cache@v2
 
-      - name: Add FuseRegistry
-        run: julia -e 'using Pkg; Pkg.Registry.add(RegistrySpec(url="https://github.com/ProjectTorreyPines/FuseRegistry.jl.git")); Pkg.Registry.add("General"); Pkg.Registry.update()'
-
       - name: Install dependencies
         run: julia --project=benchmark -e 'using Pkg; Pkg.instantiate()'
 

.github/workflows/CI.yml

@@ -36,9 +36,6 @@ jobs:
 
       - uses: julia-actions/cache@v2
 
-      - name: Add FuseRegistry
-        run: julia -e 'using Pkg; Pkg.Registry.add(RegistrySpec(url="https://github.com/ProjectTorreyPines/FuseRegistry.jl.git")); Pkg.Registry.add("General"); Pkg.Registry.update()'
-
       - uses: julia-actions/julia-buildpkg@v1
 
       - uses: julia-actions/julia-runtest@v1

.github/workflows/Documentation.yml

@@ -57,15 +57,6 @@ jobs:
 
       - uses: julia-actions/cache@v2
 
-      - name: Add FuseRegistry
-        run: |
-          rm -rf ~/.julia/registries/FuseRegistry
-          julia -e 'using Pkg; Pkg.Registry.add(RegistrySpec(url="https://github.com/ProjectTorreyPines/FuseRegistry.jl.git")); Pkg.Registry.add("General"); Pkg.Registry.update()'
-
-      - name: Replace git@github.com with https in Package.toml files
-        run: |
-          find ~/.julia/registries/FuseRegistry -type f -name 'Package.toml' -exec sed -i 's|git@github.com:|https://project-torrey-pines:${{secrets.PTP_READ_TOKEN}}@github.com/|g' {} +
-
       - name: Install dependencies
         run: |
           julia --project=docs -e '

.github/workflows/UpdateREADME.yml

@@ -42,13 +42,6 @@ jobs:
       # ──────────────────────────────────────────────────────────────
       # Benchmark Execution
       # ──────────────────────────────────────────────────────────────
-      - name: Add registries
-        run: |
-          julia -e 'using Pkg
-            Pkg.Registry.add(RegistrySpec(url="https://github.com/ProjectTorreyPines/FuseRegistry.jl.git"))
-            Pkg.Registry.add("General")
-            Pkg.Registry.update()'
-
       - name: Install benchmark dependencies
         run: julia --project=benchmark -e 'using Pkg; Pkg.instantiate()'
 

benchmark/integral_benchmark.jl

@@ -6,26 +6,26 @@ function run_integral_bench()
     y = @. sin(2pi*x) + 0.3x
 
     println("=== 1D Cubic Integration ===")
-    itp_cub = cubic_interp(x, y; extrap=:none)
+    itp_cub = cubic_interp(x, y; extrap=NoExtrap())
     print("  full-domain:  "); @btime integrate($itp_cub)
     print("  sub-range:    "); @btime integrate($itp_cub, 0.13, 0.87)
 
     println("\n=== 1D Linear Integration ===")
-    itp_lin = linear_interp(x, y; extrap=:none)
+    itp_lin = linear_interp(x, y; extrap=NoExtrap())
     print("  full-domain:  "); @btime integrate($itp_lin)
     print("  sub-range:    "); @btime integrate($itp_lin, 0.13, 0.87)
 
     println("\n=== 1D Quadratic Integration ===")
-    itp_quad = quadratic_interp(x, y; extrap=:none)
+    itp_quad = quadratic_interp(x, y; extrap=NoExtrap())
     print("  full-domain:  "); @btime integrate($itp_quad)
     print("  sub-range:    "); @btime integrate($itp_quad, 0.13, 0.87)
 
     println("\n=== Extrap modes (cubic, sub-range) ===")
-    itp_const = cubic_interp(x, y; extrap=:constant)
-    itp_wrap = cubic_interp(x, y; extrap=:wrap)
-    print("  :none      "); @btime integrate($itp_cub, 0.13, 0.87)
-    print("  :constant  "); @btime integrate($itp_const, -0.2, 1.2)
-    print("  :wrap      "); @btime integrate($itp_wrap, -0.2, 2.8)
+    itp_const = cubic_interp(x, y; extrap=ConstExtrap())
+    itp_wrap = cubic_interp(x, y; extrap=WrapExtrap())
+    print("  NoExtrap   "); @btime integrate($itp_cub, 0.13, 0.87)
+    print("  ConstExtrap"); @btime integrate($itp_const, -0.2, 1.2)
+    print("  WrapExtrap "); @btime integrate($itp_wrap, -0.2, 2.8)
 
     println("\n=== 2D Cubic Integration ===")
     xg = collect(range(0.0, 1.0, length=51))

docs/src/api/types.md

@@ -77,7 +77,6 @@ PolyFit
 LinearFit
 QuadraticFit
 CubicFit
-ParabolaFit
 ```
 
 ### Endpoint Wrappers (Quadratic Splines)

docs/src/boundary-conditions/overview.md

@@ -116,6 +116,6 @@ PeriodicBC()     # S(x) = S(x + τ) with C² continuity
 ## See Also
 
 - [PointBC Details](pointbc.md) — In-depth explanation of PolyFit with visualizations
-- [PeriodicBC Details](periodicbc.md) — Inclusive vs exclusive endpoints, period inference, comparison with `extrap=:wrap`
+- [PeriodicBC Details](periodicbc.md) — Inclusive vs exclusive endpoints, period inference, comparison with `WrapExtrap()`
 - [Quadratic Interpolation](../interpolation/quadratic.md) — BC examples in context
 - [Cubic Interpolation](../interpolation/cubic.md) — BCPair and PeriodicBC details

docs/src/boundary-conditions/periodicbc.md

@@ -4,11 +4,11 @@ True periodic boundary conditions for cubic splines, ensuring C² continuity (va
 
 ---
 
-## PeriodicBC vs `extrap=:wrap`
+## PeriodicBC vs `WrapExtrap()`
 
 These two features sound similar but solve fundamentally different problems:
 
-| | `PeriodicBC()` | `extrap=:wrap` |
+| | `PeriodicBC()` | `WrapExtrap()` |
 |---|---|---|
 | **What it does** | Solves a cyclic tridiagonal system (Sherman-Morrison) so the spline is **C² continuous** at the period boundary | Maps out-of-domain queries back into `[x₁, xₙ]` via modular arithmetic |
 | **Smoothness** | ``S, S', S''`` all match at the wrap point | No smoothness guarantee — may have jumps in value, slope, or curvature |
@@ -17,7 +17,7 @@ These two features sound similar but solve fundamentally different problems:
 | **Use case** | Physically periodic signals (angles, phases, Fourier-sampled data) | Quick "repeat" behavior without physical periodicity |
 
 !!! tip "Rule of Thumb"
-    If your data is truly periodic (e.g., one full period of `sin(x)`), use `PeriodicBC`. If you just want out-of-domain queries to wrap around, use `extrap=:wrap`.
+    If your data is truly periodic (e.g., one full period of `sin(x)`), use `PeriodicBC`. If you just want out-of-domain queries to wrap around, use `extrap=WrapExtrap()`.
 
 ---
 

docs/src/extrapolation.md

@@ -4,26 +4,34 @@ Extrapolation controls behavior when query points fall outside the data domain `
 
 ## Overview
 
-Use the `extrap` keyword argument to specify extrapolation behavior:
+All extrapolation modes are concrete subtypes of [`AbstractExtrap`](@ref). Pass them via the `extrap` keyword argument:
 
 ```julia-repl
 # One-shot: specify extrap per call
-cubic_interp(x, y, xq; extrap=:constant)
-linear_interp(x, y, xq; extrap=:extension)
+cubic_interp(x, y, xq; extrap=ConstExtrap())
+linear_interp(x, y, xq; extrap=ExtendExtrap())
 
 # Interpolant: extrap is fixed at creation
-itp = cubic_interp(x, y; extrap=:extension)  # all future calls use :extension
-itp(xq)  # uses :extension
+itp = cubic_interp(x, y; extrap=ExtendExtrap())  # all future calls use ExtendExtrap
+itp(xq)  # uses ExtendExtrap
 ```
 
-Both `linear_interp` and `cubic_interp` support the same extrapolation modes.
+All interpolation methods (`linear_interp`, `quadratic_interp`, `cubic_interp`, `constant_interp`) support the same extrapolation modes.
 
-| Mode | Behavior |
+| Type | Behavior |
 |------|----------|
-| `:none` | Throws `DomainError` (default) |
-| `:constant` | Returns boundary values |
-| `:extension` | Extends boundary polynomial |
-| `:wrap` | Wraps coordinates periodically (no smoothness enforced) |
+| [`NoExtrap()`](@ref NoExtrap) | Throws `DomainError` (default) |
+| [`ConstExtrap()`](@ref ConstExtrap) | Returns boundary values |
+| [`ExtendExtrap()`](@ref ExtendExtrap) | Extends boundary polynomial |
+| [`WrapExtrap()`](@ref WrapExtrap) | Wraps coordinates periodically (no smoothness enforced) |
+
+```
+AbstractExtrap
+├── NoExtrap       # DomainError on out-of-domain (default)
+├── ConstExtrap    # clamp to y[1] / y[end]
+├── ExtendExtrap   # continue boundary polynomial
+└── WrapExtrap     # modular coordinate mapping
+```
 
 ## Examples
 
@@ -40,64 +48,64 @@ xq = range(x[1] - 1.5, x[end] + 1.5, 300)
 nothing # hide
 ```
 
-## `extrap=:none` (Default)
+## `NoExtrap()` (Default)
 
 Throws `DomainError` for out-of-domain queries. Use when extrapolation is unexpected.
 
 ```julia
-julia> cubic_interp(x, y, -1.0; extrap=:none)  # scalar query outside domain
+julia> cubic_interp(x, y, -1.0; extrap=NoExtrap())  # scalar query outside domain
 ERROR: DomainError with -1.0:
 query point outside interpolation domain [0.0, 6.0]
 
-julia> cubic_interp(x, y, xq; extrap=:none)  # vector query (xq includes out-of-domain points)
+julia> cubic_interp(x, y, xq; extrap=NoExtrap())  # vector query (xq includes out-of-domain points)
 ERROR: DomainError with -1.5:
 query point outside interpolation domain [0.0, 6.0]
 ```
 
 Only interior queries succeed:
 
 ```@example extrap
-yq = cubic_interp(x, y, range(x[1], x[end], 200); extrap=:none)
+yq = cubic_interp(x, y, range(x[1], x[end], 200); extrap=NoExtrap())
 
-plot(title="extrap=:none", xlabel="x", ylabel="y", legend=:topright, xlims=(x[1] - 1.5, x[end] + 1.5)) # hide
+plot(title="NoExtrap()", xlabel="x", ylabel="y", legend=:topright, xlims=(x[1] - 1.5, x[end] + 1.5)) # hide
 vspan!([x[1] - 1.5, x[1]], alpha=0.1, color=:gray, label="out of domain") # hide
 vspan!([x[end], x[end] + 1.5], alpha=0.1, color=:gray, label=nothing) # hide
 plot!(range(x[1], x[end], 200), yq, label="spline", linewidth=2) # hide
 scatter!(x, y, label="data", markersize=7, color=:black) # hide
 vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) # hide
 ```
 
-## `extrap=:constant`
+## `ConstExtrap()`
 
 Returns boundary values: `y[1]` for left, `y[end]` for right.
 
 ```@example extrap
-yq = cubic_interp(x, y, xq; extrap=:constant)
+yq = cubic_interp(x, y, xq; extrap=ConstExtrap())
 
-plot(title="extrap=:constant", xlabel="x", ylabel="y", legend=:topright) # hide
+plot(title="ConstExtrap()", xlabel="x", ylabel="y", legend=:topright) # hide
 vspan!([x[1] - 1.5, x[1]], alpha=0.1, color=:gray, label="out of domain") # hide
 vspan!([x[end], x[end] + 1.5], alpha=0.1, color=:gray, label=nothing) # hide
 plot!(xq, yq, label="spline", linewidth=2) # hide
 scatter!(x, y, label="data", markersize=7, color=:black) # hide
 vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) # hide
 ```
 
-## `extrap=:extension`
+## `ExtendExtrap()`
 
 Extends the boundary polynomial beyond the domain.
 
 ```@example extrap
-yq = cubic_interp(x, y, xq; extrap=:extension)
+yq = cubic_interp(x, y, xq; extrap=ExtendExtrap())
 
-plot(title="extrap=:extension", xlabel="x", ylabel="y", legend=:topright) # hide
+plot(title="ExtendExtrap()", xlabel="x", ylabel="y", legend=:topright) # hide
 vspan!([x[1] - 1.5, x[1]], alpha=0.1, color=:gray, label="out of domain") # hide
 vspan!([x[end], x[end] + 1.5], alpha=0.1, color=:gray, label=nothing) # hide
 plot!(xq, yq, label="spline", linewidth=2) # hide
 scatter!(x, y, label="data", markersize=7, color=:black) # hide
 vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) # hide
 ```
 
-## `extrap=:wrap`
+## `WrapExtrap()`
 
 Wraps coordinates periodically:
 
@@ -111,9 +119,9 @@ This is **purely coordinate mapping**—it does not enforce any physical conditi
     If you need C² continuity at the periodic boundary, use [`bc=PeriodicBC()`](interpolation/cubic.md) with `cubic_interp`. This enforces ``S(x_1) = S(x_{\text{end}})``, ``S'(x_1) = S'(x_{\text{end}})``, and ``S''(x_1) = S''(x_{\text{end}})``.
 
 ```@example extrap
-yq = cubic_interp(x, y, xq; extrap=:wrap)
+yq = cubic_interp(x, y, xq; extrap=WrapExtrap())
 
-plot(title="extrap=:wrap", xlabel="x", ylabel="y", legend=:topright) # hide
+plot(title="WrapExtrap()", xlabel="x", ylabel="y", legend=:topright) # hide
 vspan!([x[1] - 1.5, x[1]], alpha=0.1, color=:gray, label="out of domain") # hide
 vspan!([x[end], x[end] + 1.5], alpha=0.1, color=:gray, label=nothing) # hide
 plot!(xq, yq, label="spline", linewidth=2) # hide
@@ -125,16 +133,16 @@ vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) #
 
 ```@example extrap
 # All three modes on same plot
-y_const = cubic_interp(x, y, xq; extrap=:constant)
-y_ext   = cubic_interp(x, y, xq; extrap=:extension)
-y_wrap  = cubic_interp(x, y, xq; extrap=:wrap)
+y_const = cubic_interp(x, y, xq; extrap=ConstExtrap())
+y_ext   = cubic_interp(x, y, xq; extrap=ExtendExtrap())
+y_wrap  = cubic_interp(x, y, xq; extrap=WrapExtrap())
 
 plot(title="Extrapolation Comparison", xlabel="x", ylabel="y", legend=:topright, size=(700, 400)) # hide
 vspan!([x[1] - 1.5, x[1]], alpha=0.1, color=:gray, label=nothing) # hide
 vspan!([x[end], x[end] + 1.5], alpha=0.1, color=:gray, label=nothing) # hide
-plot!(xq, y_const, label=":constant", linewidth=2) # hide
-plot!(xq, y_ext, label=":extension", linewidth=2, linestyle=:dash) # hide
-plot!(xq, y_wrap, label=":wrap", linewidth=2, linestyle=:dashdot) # hide
+plot!(xq, y_const, label="ConstExtrap", linewidth=2) # hide
+plot!(xq, y_ext, label="ExtendExtrap", linewidth=2, linestyle=:dash) # hide
+plot!(xq, y_wrap, label="WrapExtrap", linewidth=2, linestyle=:dashdot) # hide
 scatter!(x, y, label="data", markersize=7, color=:black) # hide
 vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) # hide
 ```
@@ -143,10 +151,10 @@ vline!([x[1], x[end]], color=:gray, linestyle=:dot, alpha=0.5, label=nothing) #
 
 | Mode | Behavior | Use Case |
 |------|----------|----------|
-| `:none` | `DomainError` | Strict domain enforcement (default) |
-| `:constant` | Returns boundary values | Physical constraints |
-| `:extension` | Continues boundary polynomial | Smooth continuation |
-| `:wrap` | Wraps coordinates (no smoothness) | Cyclic data (see [`PeriodicBC`](interpolation/cubic.md) for C² continuity) |
+| `NoExtrap()` | `DomainError` | Strict domain enforcement (default) |
+| `ConstExtrap()` | Returns boundary values | Physical constraints |
+| `ExtendExtrap()` | Continues boundary polynomial | Smooth continuation |
+| `WrapExtrap()` | Wraps coordinates (no smoothness) | Cyclic data (see [`PeriodicBC`](interpolation/cubic.md) for C² continuity) |
 
 ## See Also
 

docs/src/guides/autodiff_support.md

@@ -41,7 +41,7 @@ using ForwardDiff, FastInterpolations
 
 x = 0.0:0.5:5.0
 y = sin.(x)
-itp = cubic_interp(x, y; extrap=:extension)
+itp = cubic_interp(x, y; extrap=ExtendExtrap())
 
 # Compute derivative via AD
 grad = ForwardDiff.derivative(itp, 1.5)
@@ -57,7 +57,7 @@ nothing #hide
 ```@example ad
 # Series interpolant support
 y1, y2 = sin.(x), cos.(x)
-sitp = cubic_interp(x, [y1, y2]; extrap=:extension)
+sitp = cubic_interp(x, [y1, y2]; extrap=ExtendExtrap())
 grad_series = ForwardDiff.derivative(q -> sum(sitp(q)), 1.5)
 nothing #hide
 ```
@@ -85,7 +85,7 @@ using Zygote, FastInterpolations
 # Note: Use collect() to convert range to Vector for Zygote compatibility
 x = collect(0.0:0.5:5.0)
 y = 2.0 .* x .+ 1.0
-itp = linear_interp(x, y; extrap=:extension)
+itp = linear_interp(x, y; extrap=ExtendExtrap())
 
 # Single interpolant works
 grad = Zygote.gradient(itp, 1.5)[1]  # Returns 2.0
@@ -97,7 +97,7 @@ nothing #hide
 - **Complex output**: Must use `real()` or `imag()` wrapper
   ```@example zygote
   y_complex = (2.0 + 1.0im) .* x
-  itp_complex = linear_interp(x, y_complex; extrap=:extension)
+  itp_complex = linear_interp(x, y_complex; extrap=ExtendExtrap())
 
   # ❌ Zygote.gradient(itp_complex, 1.5) fails on complex output
   # ✅ Use this instead:
@@ -117,7 +117,7 @@ using Enzyme, FastInterpolations
 
 x = 0.0:0.5:5.0
 y = x .^ 2
-itp = quadratic_interp(x, y; extrap=:extension)
+itp = quadratic_interp(x, y; extrap=ExtendExtrap())
 
 # Use autodiff API
 f(xq) = itp(xq)

docs/src/guides/optimization.md

@@ -18,12 +18,12 @@ xg = range(-0.7, 1.5, length=101)
 yg = range(-0.7, 1.5, length=101)
 zg = [rosenbrock(xi, yi) for xi in xg, yi in yg]
 
-itp = cubic_interp((xg, yg), zg; extrap=:extension, bc=CubicFit())
+itp = cubic_interp((xg, yg), zg; extrap=ExtendExtrap(), bc=CubicFit())
 ```
 
-!!! tip "Why `extrap=:extension`?"
+!!! tip "Why `ExtendExtrap()`?"
     Trust-region and line-search methods may evaluate points outside the grid during
-    intermediate steps. `:extension` extrapolates smoothly from the boundary, preventing
+    intermediate steps. `ExtendExtrap()` extrapolates smoothly from the boundary, preventing
     errors without distorting the objective landscape near the boundary.
 
 ## Three Ways to Run Optimization

docs/src/interpolation/cubic.md

@@ -67,7 +67,7 @@ PeriodicBC(endpoint=:exclusive, period=2π)   # any grid → explicit period
     PeriodicBC uses the **Sherman-Morrison formula** to solve a cyclic tridiagonal system.
     This is fundamentally different from BCPair's standard tridiagonal solver.
 
-👉 See [PeriodicBC Details](../boundary-conditions/periodicbc.md) for endpoint conventions, period inference, and comparison with `extrap=:wrap`.
+👉 See [PeriodicBC Details](../boundary-conditions/periodicbc.md) for endpoint conventions, period inference, and comparison with `WrapExtrap()`.
 
 ---
 

docs/src/interpolation/derivatives.md

@@ -112,9 +112,9 @@ root = find_zero(d1, 0.5)  # Find where derivative = 0
 - **Extrapolation** settings are inherited by derivatives:
 
 ```julia
-itp = cubic_interp(x, y; extrap=:extension)
+itp = cubic_interp(x, y; extrap=ExtendExtrap())
 d1 = deriv1(itp)
-d1(-0.5)  # Uses :extension extrapolation
+d1(-0.5)  # Uses ExtendExtrap extrapolation
 ```
 
 ## API Summary