From adf4ddfe1f5627969764c1e64e750bfeeccce611 Mon Sep 17 00:00:00 2001
From: Thomas Guymer <t.m.guymer@thomasguymer.co.uk>
Date: Sat, 10 Aug 2024 11:17:00 +0100
Subject: [PATCH] add ability to use my FORTRAN implementation of the
 hypergeometric function

---
 mod_f2py.F90                    |  1 +
 mod_f2py/sub_hypergeometric.f90 | 21 +++++++++++++++++++++
 tests/func_t_CDF.py             |  7 +++++--
 tests/func_t_PDF.py             |  2 +-
 4 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 mod_f2py/sub_hypergeometric.f90

diff --git a/mod_f2py.F90 b/mod_f2py.F90
index 07737d8..f7fc12a 100644
--- a/mod_f2py.F90
+++ b/mod_f2py.F90
@@ -7,6 +7,7 @@ MODULE mod_f2py
     CONTAINS
 
     ! Include functions and subroutines ...
+    INCLUDE "mod_f2py/sub_hypergeometric.f90"
     INCLUDE "mod_f2py/sub_t_CDF.f90"
     INCLUDE "mod_f2py/sub_t_PDF.f90"
 END MODULE mod_f2py
diff --git a/mod_f2py/sub_hypergeometric.f90 b/mod_f2py/sub_hypergeometric.f90
new file mode 100644
index 0000000..28925cf
--- /dev/null
+++ b/mod_f2py/sub_hypergeometric.f90
@@ -0,0 +1,21 @@
+PURE SUBROUTINE sub_hypergeometric(a, b, c, z, ans)
+    !f2py threadsafe
+
+    ! Import standard modules ...
+    USE ISO_C_BINDING
+
+    ! Import my modules ...
+    USE mod_safe, ONLY: func_hypergeometric
+
+    IMPLICIT NONE
+
+    ! Declare inputs/outputs ...
+    REAL(kind = C_DOUBLE), INTENT(in)                                           :: a
+    REAL(kind = C_DOUBLE), INTENT(in)                                           :: b
+    REAL(kind = C_DOUBLE), INTENT(in)                                           :: c
+    REAL(kind = C_DOUBLE), INTENT(in)                                           :: z
+    REAL(kind = C_DOUBLE), INTENT(out)                                          :: ans
+
+    ! Calculate answer ...
+    ans = func_hypergeometric(a, b, c, z)
+END SUBROUTINE sub_hypergeometric
diff --git a/tests/func_t_CDF.py b/tests/func_t_CDF.py
index 482ac84..3dbaa7f 100644
--- a/tests/func_t_CDF.py
+++ b/tests/func_t_CDF.py
@@ -15,7 +15,7 @@
 from mod_f2py import mod_f2py
 
 # Define function ...
-def t_CDF(x, dof):
+def t_CDF(x, dof, /, *, fortran = True):
     """This function calculates the CDF of Student's t-distribution in the same
     way as the FORTRAN function in this repository.
     """
@@ -52,7 +52,10 @@ def t_CDF(x, dof):
         z = - (x ** 2 / dof)
 
         # Calculate CDF ...
-        ans = a + x * math.gamma(b) * scipy.special.hyp2f1(a, b, c, z) / (math.sqrt(dof * math.pi) * math.gamma(0.5 * dof))
+        if fortran:
+            ans = a + x * math.gamma(b) * mod_f2py.sub_hypergeometric(a, b, c, z) / (math.sqrt(dof * math.pi) * math.gamma(0.5 * dof))
+        else:
+            ans = a + x * math.gamma(b) * scipy.special.hyp2f1(a, b, c, z) / (math.sqrt(dof * math.pi) * math.gamma(0.5 * dof))
 
     # Return answer ...
     return ans
diff --git a/tests/func_t_PDF.py b/tests/func_t_PDF.py
index c0ff23e..860e59e 100644
--- a/tests/func_t_PDF.py
+++ b/tests/func_t_PDF.py
@@ -15,7 +15,7 @@
 from mod_f2py import mod_f2py
 
 # Define function ...
-def t_PDF(x, dof):
+def t_PDF(x, dof, /):
     """This function calculates the PDF of Student's t-distribution in the same
     way as the FORTRAN function in this repository.
     """