Provide gnc_numeric_invert() convenience function.

Clearer and faster than dividing into 1/1.

src/app-utils/gnc-sx-instance-model.c

@@ -1170,9 +1170,9 @@ create_each_transaction_helper(Transaction *template_txn, void *user_data)
                   }
                   else
                   {
-                  exchange = gnc_numeric_div(gnc_numeric_create(1,1),
+                  exchange = gnc_numeric_invert(gnc_price_get_value(price));
-                  gnc_price_get_value(price),
+                  exchange = gnc_numeric_convert(exchange, 1000,
-                  1000, GNC_HOW_RND_ROUND_HALF_UP);
+                                                 GNC_HOW_RND_ROUND_HALF_UP);
                   }
                   }
                   else
@@ -1779,4 +1779,3 @@ GHashTable* gnc_sx_all_instantiate_cashflow_all(GDate range_start, GDate range_e
                                     result_map, NULL);
     return result_map;
 }
-

src/gnome-utils/dialog-transfer.c

@@ -250,8 +250,7 @@ gnc_xfer_dialog_update_price (XferDialog *xferData)
     {
         PINFO("Found reverse price: 1 %s = %f %s", gnc_commodity_get_mnemonic(to),
               gnc_numeric_to_double(price_value), gnc_commodity_get_mnemonic(from));
-        price_value = gnc_numeric_div (gnc_numeric_create (1, 1), price_value,
+        price_value = gnc_numeric_invert(price_value);
-                                 GNC_DENOM_AUTO, GNC_HOW_DENOM_REDUCE);
     }
     else
     {
@@ -910,8 +909,7 @@ gnc_xfer_dialog_update_conv_info (XferDialog *xferData)
         gtk_label_set_text(GTK_LABEL(xferData->conv_forward), string);
         g_free(string);
 
-        rate = gnc_numeric_div(gnc_numeric_create (1, 1), rate,
+        rate = gnc_numeric_invert(rate);
-                               GNC_DENOM_AUTO, GNC_HOW_DENOM_REDUCE);
         string = g_strdup_printf("1 %s = %f %s", to_mnemonic,
                                  gnc_numeric_to_double(rate), from_mnemonic);
         gtk_label_set_text(GTK_LABEL(xferData->conv_reverse), string);
@@ -1509,8 +1507,7 @@ swap_amount (gnc_commodity **from, gnc_commodity **to, gnc_numeric *value,
     tmp_amt = from_amt;
     from_amt = to_amt;
     to_amt = tmp_amt;
-    *value = gnc_numeric_div (gnc_numeric_create(1, 1), *value,
+    *value = gnc_numeric_invert (*value);
-                              GNC_DENOM_AUTO, GNC_HOW_DENOM_REDUCE);
 }
 static void
 create_price(XferDialog *xferData, Timespec ts)
@@ -1543,12 +1540,8 @@ create_price(XferDialog *xferData, Timespec ts)
     {
         price = gnc_pricedb_lookup_day (xferData->pricedb, to, from, ts);
         if (price)
-        {
+
-            price_value = gnc_numeric_div (gnc_numeric_create(1, 1),
+            price_value = gnc_numeric_invert(gnc_price_get_value(price));
-                                           gnc_price_get_value(price),
-                                           GNC_DENOM_AUTO,
-                                           GNC_HOW_DENOM_REDUCE);
-        }
     }
 
     if (price)
@@ -1567,9 +1560,10 @@ create_price(XferDialog *xferData, Timespec ts)
             return;
         }
         if (!gnc_numeric_eq(price_value, gnc_price_get_value(price)))
-            value = gnc_numeric_div (gnc_numeric_create(1, 1), value,
+        {
-                                           PRECISION, GNC_HOW_DENOM_REDUCE);
+            value = gnc_numeric_invert(value);
-
+            value = gnc_numeric_convert(value, PRECISION, GNC_HOW_DENOM_REDUCE);
+        }
         gnc_price_begin_edit (price);
         gnc_price_set_time (price, ts);
         gnc_price_set_source (price, PRICE_SOURCE_XFER_DLG);
@@ -1788,10 +1782,9 @@ gnc_xfer_dialog_fetch (GtkButton *button, XferDialog *xferData)
         prc = gnc_pricedb_lookup_latest (xferData->pricedb, to, from);
         if (prc)
         {
-            rate = gnc_numeric_div (gnc_numeric_create (1, 1), gnc_price_get_value (prc),
-                                    GNC_DENOM_AUTO, GNC_HOW_DENOM_REDUCE);
-
             gnc_amount_edit_set_amount(GNC_AMOUNT_EDIT(xferData->price_edit), rate);
+/* FIXME: We probably want to swap the result price's to and from, not invert the price. */
+            rate = gnc_numeric_invert(gnc_price_get_value (prc));
             gnc_price_unref (prc);
             have_price = TRUE;
         }
@@ -2397,9 +2390,9 @@ gboolean gnc_xfer_dialog_run_exchange_dialog(
         gnc_numeric rate = xaccTransGetAccountConvRate(txn, reg_acc);
 
         /* XXX: should we tell the user we've done the conversion? */
-        amount = gnc_numeric_div(
+        amount = gnc_numeric_div(amount, rate,
-            amount, rate,
+                                 gnc_commodity_get_fraction(txn_cur),
-            gnc_commodity_get_fraction(txn_cur), GNC_HOW_DENOM_REDUCE);
+                                 GNC_HOW_DENOM_REDUCE);
     }
 
     /* enter the accounts */
@@ -2408,8 +2401,7 @@ gboolean gnc_xfer_dialog_run_exchange_dialog(
         gnc_xfer_dialog_select_to_currency(xfer, txn_cur);
         gnc_xfer_dialog_select_from_currency(xfer, xfer_com);
         if (!gnc_numeric_zero_p(*exch_rate))
-            *exch_rate = gnc_numeric_div(gnc_numeric_create(1, 1), *exch_rate,
+            *exch_rate = gnc_numeric_invert(*exch_rate);
-                                         GNC_DENOM_AUTO, GNC_HOW_DENOM_REDUCE);
         amount = gnc_numeric_neg(amount);
     }
     else

src/libqof/qof/gnc-numeric.c

@@ -1149,7 +1149,26 @@ gnc_numeric_to_decimal(gnc_numeric *a, guint8 *max_decimal_places)
     return TRUE;
 }
 
-
+gnc_numeric
+gnc_numeric_invert(gnc_numeric num)
+{
+    if (num.num == 0)
+        return gnc_numeric_zero();
+    if (num.denom > 0)
+    {
+        if (num.num < 0)
+            return gnc_numeric_create (-num.denom, -num.num);
+        return gnc_numeric_create (num.denom, num.num);
+    }
+    else /* Negative denominator means multiply instead of divide. */
+    {
+        int64_t mult = (num.num < 0 ? INT64_C(-1) : INT64_C(1));
+        qofint128 denom = mult128(-num.denom, mult * num.num);
+        if (denom.hi)
+            return gnc_numeric_error(GNC_ERROR_OVERFLOW);
+        return gnc_numeric_create (mult, denom.lo);
+    }
+}
 /* *******************************************************************
  *  double_to_gnc_numeric
  ********************************************************************/

src/libqof/qof/gnc-numeric.h

@@ -504,6 +504,13 @@ gnc_numeric gnc_numeric_reduce(gnc_numeric n);
  ********************************************************************/
 gboolean gnc_numeric_to_decimal(gnc_numeric * a,
                                 guint8 * max_decimal_places);
+
+/** Invert a gnc_numeric.
+ * Much faster than dividing 1 by it.
+ * @param num The number to be inverted
+ * @return a gnc_numeric that is the inverse of num
+ */
+gnc_numeric gnc_numeric_invert (gnc_numeric num);
 /** @} */
 
 /** @name GValue