Add test for building guile extensions

Guile linking was first implemented in d8fe6f7ac54f155fe5a3c33509249a70d0c816c5.
This test remained uncommitted since then because I wanted a better way to test
it, but I couldn't figure out another way to test it, so here we are.

2 files changed, 29 insertions, 0 deletions

diff --git a/Biz/Bild/Bessel.c b/Biz/Bild/Bessel.c
new file mode 100644
index 0000000..524956c
--- /dev/null
+++ b/Biz/Bild/Bessel.c
@@ -0,0 +1,19 @@
+// : dep guile-3.0
+// : lib libbessel-guile
+// : arg -shared
+// : arg -fPIC
+
+#include <math.h>
+#include <libguile.h>
+
+SCM
+j0_wrapper(SCM x)
+{
+  return scm_from_double(j0(scm_to_double(x)));
+}
+
+void
+init_bessel()
+{
+  scm_c_define_gsubr("j0", 1, 0, 0, j0_wrapper);
+}
diff --git a/Biz/Bild/Bessel.scm b/Biz/Bild/Bessel.scm
new file mode 100644
index 0000000..ad40834
--- /dev/null
+++ b/Biz/Bild/Bessel.scm
@@ -0,0 +1,10 @@
+;; : out bessel.exe
+(import (only (rnrs base) assert))
+(load-extension "libguile-bessel" "init_bessel")
+(define (main args)
+  (let ((result (j0 2)))
+    (display "testing")
+    (newline)
+    (display result)
+    (newline)
+    (assert (= (j0 2) 0.22389077914123567))))