From 107097c439378803dafbea63e90b0029b53b5e58 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8C=97=E9=9C=B2?=
 <69190413+illusory0x0@users.noreply.github.com>
Date: Tue, 1 Jul 2025 19:05:57 +0800
Subject: [PATCH] feat(bigint): add `BigInt::to_int16` and `BitInt::to_uint16`

---
 bigint/bigint.mbt  | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 bigint/bigint.mbti |  2 ++
 2 files changed, 50 insertions(+)

diff --git a/bigint/bigint.mbt b/bigint/bigint.mbt
index 63d828ce9..e29ae82b6 100644
--- a/bigint/bigint.mbt
+++ b/bigint/bigint.mbt
@@ -234,3 +234,51 @@ fn BigInt::signum(self : Self) -> Int {
     1
   }
 }
+
+///|
+/// Converts a `BigInt` value to an unsigned 16-bit integer (`UInt16`).
+///
+/// Parameters:
+///
+/// * `self` : The `BigInt` value to be converted.
+///
+/// Returns a `UInt16` value representing the lower 16 bits of the input
+/// `BigInt`.
+///
+/// Example:
+///
+/// ```moonbit
+/// let n = 42N
+/// inspect(n.to_uint16(), content="42")
+/// let neg = -1N
+/// inspect(neg.to_uint16(), content="65535") // 2^16 - 1
+/// ```
+///
+pub fn BigInt::to_uint16(self : BigInt) -> UInt16 {
+  self.to_int().to_uint16()
+}
+
+///|
+/// Converts a `BigInt` value to a signed 16-bit integer (`Int16`).
+///
+/// Parameters:
+///
+/// * `self` : The `BigInt` value to be converted.
+///
+/// Returns a 16-bit signed integer representing the lower 16 bits of the input
+/// `BigInt`.
+///
+/// Example:
+///
+/// ```moonbit
+/// let n = 42N
+/// inspect(n.to_int16(), content="42")
+/// let neg = -1N
+/// inspect(neg.to_int16(), content="-1")
+/// let big = 32768N // 2^15
+/// inspect(big.to_int16(), content="-32768") // Overflow to Int16.min_value
+/// ```
+///
+pub fn BigInt::to_int16(self : BigInt) -> Int16 {
+  self.to_int().to_int16()
+}
diff --git a/bigint/bigint.mbti b/bigint/bigint.mbti
index 50f33d037..ffd6573bf 100644
--- a/bigint/bigint.mbti
+++ b/bigint/bigint.mbti
@@ -33,10 +33,12 @@ fn BigInt::shl(Self, Int) -> Self
 fn BigInt::shr(Self, Int) -> Self
 fn BigInt::to_hex(Self, uppercase~ : Bool = ..) -> String
 fn BigInt::to_int(Self) -> Int
+fn BigInt::to_int16(Self) -> Int16
 fn BigInt::to_int64(Self) -> Int64
 fn BigInt::to_octets(Self, length? : Int) -> Bytes
 fn BigInt::to_string(Self) -> String
 fn BigInt::to_uint(Self) -> UInt
+fn BigInt::to_uint16(Self) -> UInt16
 fn BigInt::to_uint64(Self) -> UInt64
 impl Add for BigInt
 impl BitAnd for BigInt