Public API cleanup: umbrella module re-exports and missing methods

Re-export constants, error flags, fitting flags, and utility functions
from the fitpack umbrella module so users need only `use fitpack`.

Add missing methods across types:
- eval/eval_ongrid on fitpack_surface (scattered via bispeu, grid via bispev)
- interpolate/least_squares on fitpack_surface
- least_squares on fitpack_curve
- mse on all 6 surface/polar/sphere types

Author: perazz

.claude/settings.local.json

@@ -7,7 +7,10 @@
       "Bash(git add:*)",
       "Bash(git commit:*)",
       "Bash(git checkout:*)",
-      "Bash(git push:*)"
+      "Bash(git push:*)",
+      "Bash(grep:*)",
+      "Bash(fpm build:*)",
+      "Bash(git status:*)"
     ],
     "deny": [],
     "ask": []

src/fitpack.f90

@@ -32,12 +32,13 @@ module fitpack
    implicit none
    private
 
-   ! Public interface
+   ! Public interface: kind parameters
    public :: FP_REAL
    public :: FP_SIZE
    public :: FP_FLAG
    public :: FP_BOOL
 
+   ! Public interface: types
    public :: fitpack_curve
    public :: fitpack_closed_curve
    public :: fitpack_periodic_curve
@@ -54,5 +55,24 @@ module fitpack
    public :: fitpack_grid_surface
    public :: fitpack_parametric_surface
 
+   ! Public interface: boundary behavior flags
+   public :: OUTSIDE_EXTRAPOLATE, OUTSIDE_ZERO, OUTSIDE_NOT_ALLOWED, OUTSIDE_NEAREST_BND
+
+   ! Public interface: fitting state flags
+   public :: IOPT_NEW_LEASTSQUARES, IOPT_NEW_SMOOTHING, IOPT_OLD_FIT
+
+   ! Public interface: error flags
+   public :: FITPACK_OK, FITPACK_INTERPOLATING_OK, FITPACK_LEASTSQUARES_OK
+   public :: FITPACK_INSUFFICIENT_STORAGE, FITPACK_S_TOO_SMALL, FITPACK_MAXIT
+   public :: FITPACK_TOO_MANY_KNOTS, FITPACK_OVERLAPPING_KNOTS, FITPACK_INVALID_RANGE
+   public :: FITPACK_INPUT_ERROR, FITPACK_TEST_ERROR
+   public :: FITPACK_INVALID_CONSTRAINT, FITPACK_INSUFFICIENT_KNOTS
+
+   ! Public interface: error utility functions
+   public :: FITPACK_SUCCESS, FITPACK_MESSAGE, IOPT_MESSAGE
+
+   ! Public interface: named constants
+   public :: zero, one, half, pi
+
 
 end module fitpack

src/fitpack_curves.f90

@@ -81,8 +81,9 @@ module fitpack_curves
            procedure :: new_fit
 
            !> Generate/update fitting curve, with optional smoothing
-           procedure :: fit         => curve_fit_automatic_knots
-           procedure :: interpolate => interpolating_curve
+           procedure :: fit           => curve_fit_automatic_knots
+           procedure :: interpolate   => interpolating_curve
+           procedure :: least_squares => curve_fit_least_squares
 
            !> Evaluate curve at given coordinates
            procedure, private :: curve_eval_one
@@ -363,6 +364,13 @@ integer(FP_FLAG) function interpolating_curve(this,order) result(ierr)
 
     end function interpolating_curve
 
+    ! Least-squares curve fit with current knots
+    integer(FP_FLAG) function curve_fit_least_squares(this) result(ierr)
+        class(fitpack_curve), intent(inout) :: this
+        this%iopt = IOPT_NEW_LEASTSQUARES
+        ierr = this%fit()
+    end function curve_fit_least_squares
+
     ! Curve fitting driver: automatic number of knots
     integer(FP_FLAG) function curve_fit_automatic_knots(this,smoothing,order) result(ierr)
         class(fitpack_curve), intent(inout) :: this

src/fitpack_grid_surfaces.f90

@@ -92,6 +92,9 @@ module fitpack_grid_surfaces
            generic   :: dfdx => gridded_derivatives_one,gridded_derivatives_many
            generic   :: dfdx_ongrid => gridded_derivatives_gridded
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => gridsurf_error
+
     end type fitpack_grid_surface
 
     interface fitpack_grid_surface
@@ -458,4 +461,10 @@ real(FP_REAL) function gridded_derivatives_one(this,x,y,dx,dy,ierr) result(f)
 
     end function gridded_derivatives_one
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function gridsurf_error(this)
+       class(fitpack_grid_surface), intent(in) :: this
+       gridsurf_error = this%fp
+    end function gridsurf_error
+
 end module fitpack_grid_surfaces

src/fitpack_gridded_polar.f90

@@ -102,6 +102,9 @@ module fitpack_gridded_polar
            procedure, private :: gridded_eval_many
            generic :: eval => gridded_eval_one,gridded_eval_many
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => gridpolar_error
+
            !> Write to disk
            procedure :: write => gridded_to_disk
 
@@ -389,4 +392,10 @@ end function numbered
 
     end subroutine gridded_to_disk
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function gridpolar_error(this)
+       class(fitpack_grid_polar), intent(in) :: this
+       gridpolar_error = this%fp
+    end function gridpolar_error
+
 end module fitpack_gridded_polar

src/fitpack_gridded_sphere.f90

@@ -95,6 +95,9 @@ module fitpack_gridded_sphere
            procedure, private :: gridded_eval_many
            generic :: eval => gridded_eval_one,gridded_eval_many
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => gridsphere_error
+
            !> Write to disk
            procedure :: write => gridded_to_disk
 
@@ -396,4 +399,10 @@ end function numbered
 
     end subroutine gridded_to_disk
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function gridsphere_error(this)
+       class(fitpack_grid_sphere), intent(in) :: this
+       gridsphere_error = this%fp
+    end function gridsphere_error
+
 end module fitpack_gridded_sphere

src/fitpack_polar.f90

@@ -103,6 +103,9 @@ module fitpack_polar_domains
            procedure, private :: polr_eval_many
            generic :: eval => polr_eval_one,polr_eval_many
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => polar_error
+
     end type fitpack_polar
 
     interface fitpack_polar
@@ -342,4 +345,10 @@ integer function polr_new_fit(this,x,y,z,boundary,w,boundary_bc,smoothing)
 
     end function polr_new_fit
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function polar_error(this)
+       class(fitpack_polar), intent(in) :: this
+       polar_error = this%fp
+    end function polar_error
+
 end module fitpack_polar_domains

src/fitpack_spheres.f90

@@ -84,6 +84,9 @@ module fitpack_sphere_domains
            procedure, private :: sphere_eval_many
            generic :: eval => sphere_eval_one,sphere_eval_many
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => sphere_error
+
     end type fitpack_sphere
 
     interface fitpack_sphere
@@ -302,4 +305,10 @@ integer function sphere_new_fit(this,theta,phi,r,w,smoothing)
 
     end function sphere_new_fit
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function sphere_error(this)
+       class(fitpack_sphere), intent(in) :: this
+       sphere_error = this%fp
+    end function sphere_error
+
 end module fitpack_sphere_domains

src/fitpack_surfaces.f90

@@ -78,7 +78,18 @@ module fitpack_surfaces
            procedure :: new_fit    => surf_new_fit
 
            !> Generate/update fitting curve, with optional smoothing
-           procedure :: fit        => surface_fit_automatic_knots
+           procedure :: fit           => surface_fit_automatic_knots
+           procedure :: interpolate   => surface_fit_interpolating
+           procedure :: least_squares => surface_fit_least_squares
+
+           !> Evaluate surface at given coordinates
+           procedure, private :: surface_eval_one
+           procedure, private :: surface_eval_many
+           generic   :: eval => surface_eval_one,surface_eval_many
+
+           !> Evaluate surface on a grid
+           procedure, private :: surface_eval_gridded
+           generic   :: eval_ongrid => surface_eval_gridded
 
            !> Evaluate derivatives at given coordinates
            procedure, private :: surface_derivatives_gridded
@@ -87,6 +98,9 @@ module fitpack_surfaces
            generic   :: dfdx => surface_derivatives_one,surface_derivatives_many
            generic   :: dfdx_ongrid => surface_derivatives_gridded
 
+           !> Properties: MSE
+           procedure, non_overridable :: mse => surface_error
+
     end type fitpack_surface
 
     interface fitpack_surface
@@ -144,6 +158,104 @@ integer(FP_FLAG) function surface_fit_automatic_knots(this,smoothing,order) resu
     end function surface_fit_automatic_knots
 
 
+    ! Find interpolating surface
+    integer(FP_FLAG) function surface_fit_interpolating(this) result(ierr)
+        class(fitpack_surface), intent(inout) :: this
+        ierr = surface_fit_automatic_knots(this,smoothing=zero)
+    end function surface_fit_interpolating
+
+    ! Fit a surface to least squares of the current knots
+    integer(FP_FLAG) function surface_fit_least_squares(this) result(ierr)
+       class(fitpack_surface), intent(inout) :: this
+       this%iopt = IOPT_NEW_LEASTSQUARES
+       ierr = this%fit()
+    end function surface_fit_least_squares
+
+    !> Evaluate surface on a list of (x(i),y(i)) scattered points using bispeu
+    function surface_eval_many(this,x,y,ierr) result(f)
+        class(fitpack_surface), intent(inout) :: this
+        real(FP_REAL), intent(in) :: x(:),y(size(x))
+        real(FP_REAL) :: f(size(x))
+        integer(FP_FLAG), optional, intent(out) :: ierr
+
+        integer(FP_FLAG) :: ier
+        integer(FP_SIZE) :: min_lwrk
+        real(FP_REAL), allocatable :: wrk(:)
+
+        ! bispeu workspace: lwrk >= kx+ky+2
+        min_lwrk = sum(this%order) + 2
+        allocate(wrk(min_lwrk))
+
+        call bispeu(tx=this%t(:,1),nx=this%knots(1),   &
+                    ty=this%t(:,2),ny=this%knots(2),   &
+                    c=this%c,                          &
+                    kx=this%order(1),ky=this%order(2), &
+                    x=x,y=y,z=f,m=size(x),            &
+                    wrk=wrk,lwrk=min_lwrk,             &
+                    ier=ier)
+
+        call fitpack_error_handling(ier,ierr,'evaluate bivariate surface')
+
+    end function surface_eval_many
+
+    !> Evaluate surface at a single (x,y) point
+    real(FP_REAL) function surface_eval_one(this,x,y,ierr) result(f)
+        class(fitpack_surface), intent(inout) :: this
+        real(FP_REAL), intent(in) :: x,y
+        integer(FP_FLAG), optional, intent(out) :: ierr
+
+        real(FP_REAL) :: z1(1)
+
+        z1 = surface_eval_many(this,[x],[y],ierr)
+        f  = z1(1)
+
+    end function surface_eval_one
+
+    !> Evaluate surface on a grid domain using bispev
+    function surface_eval_gridded(this,x,y,ierr) result(f)
+        class(fitpack_surface), intent(inout) :: this
+        real(FP_REAL), intent(in) :: x(:),y(:)
+        real(FP_REAL) :: f(size(y),size(x))
+        integer(FP_FLAG), optional, intent(out) :: ierr
+
+        integer(FP_FLAG) :: ier
+        integer(FP_SIZE) :: min_lwrk,min_kwrk,m(2)
+        real(FP_REAL), allocatable :: min_wrk(:)
+        integer(FP_SIZE), allocatable :: min_iwrk(:)
+
+        m = [size(x),size(y)]
+
+        ! Assert real working storage
+        min_lwrk = sum(m*(this%order+1)) + product(this%knots-this%order-1)
+        if (min_lwrk>this%lwrk1) then
+            allocate(min_wrk(min_lwrk),source=0.0_FP_REAL)
+            call move_alloc(from=min_wrk,to=this%wrk1)
+            this%lwrk1 = min_lwrk
+        end if
+
+        ! Assert integer working storage
+        min_kwrk = sum(m)
+        if (min_kwrk>this%liwrk) then
+            allocate(min_iwrk(min_kwrk),source=0_FP_SIZE)
+            call move_alloc(from=min_iwrk,to=this%iwrk)
+            this%liwrk = min_kwrk
+        end if
+
+        call bispev(tx=this%t(:,1),nx=this%knots(1),   &
+                    ty=this%t(:,2),ny=this%knots(2),   &
+                    c=this%c,                          &
+                    kx=this%order(1),ky=this%order(2), &
+                    x=x,mx=size(x),                    &
+                    y=y,my=size(y),                    &
+                    z=f,                               &
+                    wrk=this%wrk1,lwrk=this%lwrk1,     &
+                    iwrk=this%iwrk,kwrk=this%liwrk,    &
+                    ier=ier)
+
+        call fitpack_error_handling(ier,ierr,'evaluate gridded surface')
+
+    end function surface_eval_gridded
+
     elemental subroutine surf_destroy(this)
        class(fitpack_surface), intent(inout) :: this
        integer :: ierr
@@ -424,4 +536,10 @@ real(FP_REAL) function surface_derivatives_one(this,x,y,dx,dy,ierr) result(f)
     end function surface_derivatives_one
 
 
+    ! Return fitting MSE
+    elemental real(FP_REAL) function surface_error(this)
+       class(fitpack_surface), intent(in) :: this
+       surface_error = this%fp
+    end function surface_error
+
 end module fitpack_surfaces