+SCM
+Prob::equal_p (SCM sa, SCM sb)
+{
+ /* This comparison function is only designed to make the copy
+ constructor preserve equality.
+
+ Perhaps it would be better to use a more strict definition of
+ equality; e.g., that two probs are equal iff they can be
+ distinguished by calls to ly:prob-property.
+ */
+ Prob *probs[2] = {unsmob<Prob> (sa), unsmob<Prob> (sb)};
+ SCM props[2][2];
+ int i;
+
+ for (i = 0; i < 2; i++)
+ {
+ props[i][0] = probs[i]->immutable_property_alist_;
+ props[i][1] = probs[i]->mutable_property_alist_;
+ }
+
+ if (strcmp (probs[0]->class_name (), probs[1]->class_name ()))
+ return SCM_BOOL_F;
+
+ /* Compare mutable and immutable lists, element by element. */
+ for (i = 0; i < 2; i++)
+ {
+ SCM aprop = props[0][i];
+ SCM bprop = props[1][i];
+
+ for (;
+ scm_is_pair (aprop) && scm_is_pair (bprop);
+ aprop = scm_cdr (aprop), bprop = scm_cdr (bprop))
+ {
+ SCM aval = scm_cdar (aprop);
+ SCM bval = scm_cdar (bprop);
+ if (!scm_is_eq (scm_caar (aprop), scm_caar (bprop))
+ || (!(unsmob<Input> (aval) && unsmob<Input> (bval))
+ && !ly_is_equal (aval, bval)))
+ return SCM_BOOL_F;
+ }
+
+ /* is one list shorter? */
+ if (!scm_is_null (aprop) || !scm_is_null (bprop))
+ return SCM_BOOL_F;
+ }
+
+ return SCM_BOOL_T;
+}