From 25343d3723ae70690f056b0a501f5941892fbf93 Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Tue, 23 Feb 2021 16:24:48 +0530
Subject: Provide test integrals.

* include/integrands.h, src/integrands.sc: New files.
---
 include/integrands.h | 15 +++++++++++++++
 src/integrands.sc    | 19 +++++++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 include/integrands.h
 create mode 100644 src/integrands.sc

diff --git a/include/integrands.h b/include/integrands.h
new file mode 100644
index 0000000..b4735a8
--- /dev/null
+++ b/include/integrands.h
@@ -0,0 +1,15 @@
+#ifndef INTEGRANDS_H
+#define INTEGRANDS_H
+
+#include <gsl/gsl_vector.h>
+
+typedef struct {
+  double *coefficients;
+  int degree;
+} polynomial_integrand_params;
+
+double polynomial_integrand (double r, const gsl_vector* x, void *params);
+double gaussian_integrand (double r, const gsl_vector* x, void *params);
+double x_coordinate_integrand (double r, const gsl_vector* x, void *params);
+
+#endif
diff --git a/src/integrands.sc b/src/integrands.sc
new file mode 100644
index 0000000..750530c
--- /dev/null
+++ b/src/integrands.sc
@@ -0,0 +1,19 @@
+(pre-include "gsl/gsl_math.h")
+(pre-include "gsl/gsl_poly.h")
+(pre-include "integrands.h")
+
+(define (polynomial-integrand r x -params) (double double (const gsl-vector*) void*)
+  (let* ((params polynomial-integrand-params*
+                 (convert-type -params polynomial-integrand-params*)))
+    (return (gsl-poly-eval (: params coefficients)
+                           (+ (: params degree) 1)
+                           r))))
+
+(define (gaussian-integrand r x -params) (double double (const gsl-vector*) void*)
+  ;; This is a workaround to fix negation bug in sph-sc. See
+  ;; https://github.com/sph-mn/sph-sc/issues/5 . TODO: Remove
+  ;; workaround once bug is fixed upstream.
+  (return (exp (- 0 (/ (gsl-pow-2 r) 2)))))
+
+(define (x-coordinate-integrand r x -params) (double double (const gsl-vector*) void*)
+  (return (fabs (* r (gsl-vector-get x 0)))))
-- 
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