From 98329e0a3dd4f78b5d815ac3896272ec70904901 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Thu, 11 Dec 2025 10:28:11 +0100
Subject: Add remaining haskell book exercises

---
 Haskell-book/24/ParserExercises/src/SemVer.hs | 51 +++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Haskell-book/24/ParserExercises/src/SemVer.hs

(limited to 'Haskell-book/24/ParserExercises/src/SemVer.hs')

diff --git a/Haskell-book/24/ParserExercises/src/SemVer.hs b/Haskell-book/24/ParserExercises/src/SemVer.hs
new file mode 100644
index 0000000..47b49ab
--- /dev/null
+++ b/Haskell-book/24/ParserExercises/src/SemVer.hs
@@ -0,0 +1,51 @@
+module SemVer where
+
+import Control.Applicative
+import Text.Trifecta
+
+-- 1. Write a parser for semantic versions as defined by http://semver.org/.
+-- After making a working parser, write an Ord instance for the SemVer type
+-- that obeys the specification outlined on the SemVer website.
+
+-- Relevant to precedence/ordering,
+-- cannot sort numbers like strings.
+data NumberOrString = NOSS String
+                    | NOSI Integer
+                    deriving (Eq, Show)
+
+type Major = Integer
+type Minor = Integer
+type Patch = Integer
+type Release = [NumberOrString]
+type Metadata = [NumberOrString]
+
+data SemVer = SemVer Major Minor Patch Release Metadata
+    deriving (Eq, Show)
+
+parseNos :: Parser NumberOrString
+parseNos = do
+    nos <- (NOSI <$> integer)
+       <|> (NOSS <$> some letter)
+    return nos
+
+parseRelease :: Parser [NumberOrString]
+parseRelease = do
+    _ <- char '-'
+    sepBy parseNos (char '.')
+
+parseMetadata :: Parser [NumberOrString]
+parseMetadata = do
+    _ <- char '+'
+    sepBy parseNos (char '.')
+
+parseSemVer :: Parser SemVer
+parseSemVer = do
+    major <- decimal
+    _ <- char '.'
+    minor <- decimal
+    _ <- char '.'
+    patch <- decimal
+    release <- option [] parseRelease
+    metadata <- option [] parseMetadata
+
+    return $ SemVer major minor patch release metadata
-- 
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