From a495386ec95e80813f34a1e02bbedbc636ff653f Mon Sep 17 00:00:00 2001
From: Clemens Schmid <clemens@nevrome.de>
Date: Mon, 20 Nov 2023 11:22:38 +0100
Subject: [PATCH] added a check to make sure the age ranges are the right way
 around

---
 src/Currycarbon/Parsers.hs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/Currycarbon/Parsers.hs b/src/Currycarbon/Parsers.hs
index 67c8249..55fc3b6 100644
--- a/src/Currycarbon/Parsers.hs
+++ b/src/Currycarbon/Parsers.hs
@@ -118,7 +118,9 @@ parseTimeWindowBP = do
     start <- parsePositiveInteger
     _ <- P.spaces *> P.string "<-|" <* P.spaces
     stop <- parsePositiveInteger
-    return (TimeWindowBP name start stop)
+    if start >= stop
+    then return (TimeWindowBP name start stop)
+    else fail "the BP stop date can not be larger then the start date"
 
 parseTimeWindowBCAD :: P.Parser TimeWindowBCAD
 parseTimeWindowBCAD = do
@@ -127,7 +129,9 @@ parseTimeWindowBCAD = do
     start <- parseInteger
     _ <- P.spaces *> P.string "<+>" <* P.spaces
     stop <- parseInteger
-    return (TimeWindowBCAD name start stop)
+    if start <= stop
+    then return (TimeWindowBCAD name start stop)
+    else fail "the BC/AD stop date can not be smaller then the start date"
 
 add :: P.Parser CalExpr
 add = SumCal <$> term <*> (spaceChar '+' *> expr)