From a45f29178afd4d1d1336316ad86df6cb4e89664a Mon Sep 17 00:00:00 2001
From: Sam HADOW <sam.hadow@inbox.lv>
Date: Mon, 12 Jan 2026 13:47:05 +0100
Subject: [PATCH] modular square root UI

---
 app/Main.hs                |  5 +++--
 app/ModularSquareRootUI.hs | 20 ++++++++++++++++++++
 haskell-math.cabal         |  1 +
 3 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 app/ModularSquareRootUI.hs

diff --git a/app/Main.hs b/app/Main.hs
index 76a68fa..adf224c 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -2,19 +2,20 @@ module Main where
 
 import Utils (askChoice)
 import qualified FactorizationUI
+import qualified ModularSquareRootUI
 import qualified PrimesUI
 
 main :: IO ()
 main = do
     putStrLn "Haskell Math Toolkit"
     putStrLn "1) Factorization"
-    putStrLn "2) Modular square root (not yet implemented)"
+    putStrLn "2) Modular square root"
     putStrLn "3) Primality tests"
 
     choice <- askChoice 3
 
     case choice of
         1 -> FactorizationUI.run
-        2 -> putStrLn "Modular square root: not implemented yet."
+        2 -> ModularSquareRootUI.run
         3 -> PrimesUI.run
         _ -> error "Impossible"
diff --git a/app/ModularSquareRootUI.hs b/app/ModularSquareRootUI.hs
new file mode 100644
index 0000000..6e3d2df
--- /dev/null
+++ b/app/ModularSquareRootUI.hs
@@ -0,0 +1,20 @@
+module ModularSquareRootUI (run) where
+
+import Utils (askNumber)
+import ModularSquareRoot (tonelliShanks)
+
+run :: IO ()
+run = do
+    putStrLn "Modular square root (Tonelli–Shanks)"
+    putStrLn "Solve x^2 = n (mod p), with p an odd prime."
+
+    n <- askNumber "Enter n:"
+    p <- askNumber "Enter prime modulus p:"
+
+    case tonelliShanks n p of
+        Just x -> do
+            putStrLn "Solution found:"
+            putStrLn ("x = " ++ show x ++ " (mod " ++ show p ++ ")")
+            putStrLn ("Other root: " ++ show ((p - x) `mod` p))
+        Nothing ->
+            putStrLn "No square root exists modulo p."
diff --git a/haskell-math.cabal b/haskell-math.cabal
index 32c6a5f..2e7a385 100644
--- a/haskell-math.cabal
+++ b/haskell-math.cabal
@@ -42,6 +42,7 @@ executable haskell-math
     other-modules:
         FactorizationUI
         PrimesUI
+        ModularSquareRootUI
         Utils
     build-depends:
         base ^>=4.18.2.1,