Flipping coins.

Applying one or more gold pieces now flips one of them, which will
cause it to come up heads or tails. This is NetHack, so there are
special cases for flipping a coin underwater or while fumbling or
greasy.

I've tried to future-proof this commit so that the code will not
need to be modified if other items are eventually added to the
coin class.

If memory serves, there was a patch for this on the bilious patch
database, but I was unable to locate it or who the original author
was. In any case, the code is entirely original.

src/apply.c

@@ -40,6 +40,7 @@ static int use_grapple(struct obj *);
 static int do_break_wand(struct obj *);
 static int apply_ok(struct obj *);
 static int flip_through_book(struct obj *);
+static int flip_coin(struct obj *);
 static boolean figurine_location_checks(struct obj *, coord *, boolean);
 static boolean check_jump(genericptr_t, coordxy, coordxy);
 static boolean is_valid_jump_pos(coordxy, coordxy, int, boolean);
@@ -3966,6 +3967,11 @@ apply_ok(struct obj *obj)
         || obj->oclass == SPBOOK_CLASS)
         return GETOBJ_SUGGEST;
 
+    /* applying coins to flip them is a minor easter egg, so do not suggest
+       coin application to the player */
+    if (obj->oclass == COIN_CLASS)
+        return GETOBJ_DOWNPLAY;
+
     /* certain weapons */
     if (obj->oclass == WEAPON_CLASS
         && (is_pick(obj) || is_axe(obj) || is_pole(obj)
@@ -4036,6 +4042,9 @@ doapply(void)
     if (obj->oclass == SPBOOK_CLASS)
         return flip_through_book(obj);
 
+    if (obj->oclass == COIN_CLASS)
+        return flip_coin(obj);
+
     switch (obj->otyp) {
     case BLINDFOLD:
     case LENSES:
@@ -4312,4 +4321,36 @@ flip_through_book(struct obj *obj)
     return ECMD_TIME;
 }
 
+static int
+flip_coin(struct obj *obj)
+{
+    struct obj *otmp = obj;
+    boolean lose_coin = FALSE;
+
+    You("flip %s.", an(cxname_singular(obj)));
+    if (Underwater) {
+        pline_The("%s floats away.", xname(obj));
+        lose_coin = TRUE;
+    } else if (Glib || Fumbling || (ACURR(A_DEX) < 10 && !rn2(ACURR(A_DEX)))) {
+        pline_The("%s slips between your %s.", xname(obj),
+              fingers_or_gloves(FALSE));
+        lose_coin = TRUE;
+    }
+
+    if (lose_coin) {
+        if (otmp->quan > 1L)
+            otmp = splitobj(otmp, 1L);
+        dropx(otmp);
+        return ECMD_TIME;
+    }
+    if (Hallucination) {
+        pline(rn2(100) ? "Wow, a double header!"
+                        /* edge case */
+                       : "The coin miraculously lands on its edge!");
+    } else {
+        pline("It comes up %s.", rn2(2) ? "heads" : "tails");
+    }
+    return ECMD_TIME;
+}
+
 /*apply.c*/

src/invent.c

@@ -2941,7 +2941,9 @@ itemactions(struct obj *otmp)
     }
 
     /* a: apply */
-    if (otmp->otyp == CREAM_PIE)
+    if (otmp->oclass == COIN_CLASS)
+        ia_addmenu(win, IA_APPLY_OBJ, 'a', "Flip a coin");
+    else if (otmp->otyp == CREAM_PIE)
         ia_addmenu(win, IA_APPLY_OBJ, 'a', "Hit yourself with this cream pie");
     else if (otmp->otyp == BULLWHIP)
         ia_addmenu(win, IA_APPLY_OBJ, 'a', "Lash out with this whip");