--- a
+++ b/pre_install.m
@@ -0,0 +1,26 @@
+function pre_install(desc)
+# Sets FENV_OPTS variable for the Makefile
+# If the system is detected as an x86/x86_64 machine, we define a flag which
+# is later used when compiling system_dependent.cc
+
+systemtype = computer();
+
+# Presently, we support either x86_64...
+supported = ~isempty(findstr('x86_64', systemtype));
+
+# or x86...
+# 	(Actually we only support i486DX and above, 
+# 	but in many cases the default compiler settings are for i386.
+# 	We also do believe older machines are already either dead 
+#	or at the museum.)
+supported |= strcmp("i86", systemtype([1,3,4]));
+
+file = fopen('src/configure.in','wt');
+fprintf(file,'FENV_OPTS = ');
+if (supported)
+	fprintf(file,'-DX86_PROCESSOR');
+end
+fprintf(file,'\n');
+fclose(file);
+
+endfunction