addid library source 20140221

[zither/ds-zither.git] / sources / lib / libms / month_minus.c

diff --git a/sources/lib/libms/month_minus.c b/sources/lib/libms/month_minus.c
new file mode 100644 (file)
index 0000000..c4fe7b1
--- /dev/null
+++ b/sources/lib/libms/month_minus.c
@@ -0,0 +1,29 @@
+
+
+
+// 指定月から一ヶ月引いた月をかえす。単純。。。
+int month_minus(int month)
+{
+int ret;
+ret = -1;
+
+switch(month){
+   case 1: ret = 12;  break;
+   case 2: ret = 1;   break;
+   case 3: ret = 2;   break;
+   case 4: ret = 3;   break;
+   case 5: ret = 4;   break;
+   case 6: ret = 5;   break;
+   case 7: ret = 6;   break;
+   case 8: ret = 7;   break;
+   case 9: ret = 8;   break;
+   case 10: ret = 9;  break;
+   case 11: ret = 10; break;
+   case 12: ret = 11; break;
+   default: ret = 0; break;
+   }
+
+return ret;
+}
+
+