From c38e321192779fa7fdfeb290e4c08460d1595cdc Mon Sep 17 00:00:00 2001
From: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Date: Sun, 13 Sep 2026 09:21:41 -0400
Subject: [PATCH] Support mixed scalar inputs in buffered BigInt arithmetic

Convert Scaling inputs for buffered add/sub-multiply as in the unbuffered
implementation, fixing mixed rational subtraction and preserving aliases.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Codex <noreply@openai.com>
Agent-Harness: Codex CLI 0.154.0
Agent-Model: gpt-6-astra
Agent-Session: local session ID 01a099aa-308a-7fd3-91bd-9fb2dc357b91
---
 src/implementations/BigInt.jl | 20 +++++++++++++++++++
 test/test_big.jl              | 36 +++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/src/implementations/BigInt.jl b/src/implementations/BigInt.jl
index 4bf0966..f8bd865 100644
--- a/src/implementations/BigInt.jl
+++ b/src/implementations/BigInt.jl
@@ -227,6 +227,26 @@ function operate_to!(
     )
 end
 
+function buffered_operate_to!(
+    buffer::BigInt,
+    output::BigInt,
+    op::AddSubMul,
+    x::Scaling,
+    y::Scaling,
+    z::Scaling,
+    args::Vararg{Scaling,N},
+) where {N}
+    return buffered_operate_to!(
+        buffer,
+        output,
+        op,
+        _scaling_to_bigint(x),
+        _scaling_to_bigint(y),
+        _scaling_to_bigint(z),
+        _scaling_to_bigint.(args)...,
+    )
+end
+
 # Called for instance if `args` is `(v', v)` for a vector `v`.
 function operate_to!(
     output::BigInt,
diff --git a/test/test_big.jl b/test/test_big.jl
index 96d28a0..9cd8672 100644
--- a/test/test_big.jl
+++ b/test/test_big.jl
@@ -317,6 +317,42 @@ function test_alloc()
     return
 end
 
+function test_buffered_BigInt_mixed_integers()
+    for op in (MA.add_mul, MA.sub_mul),
+        args in ((big(2), 3, big(4)), (2, big(3), 4), (big(2), 3, big(4), 5))
+
+        expected = op(big.(args)...)
+        original = deepcopy(args)
+        output, buffer = big(0), big(0)
+        @test MA.buffered_operate_to!(buffer, output, op, args...) === output
+        @test output == expected
+        @test args == original
+    end
+    for op in (MA.add_mul, MA.sub_mul)
+        expected = op(big(2), big(3), big(4))
+        output, buffer = big(2), big(4)
+        @test MA.buffered_operate!(buffer, op, output, 3, buffer) === output
+        @test output == expected
+        output = big(0)
+        @test MA.buffered_operate_to!(output, output, op, big(2), 3, big(4)) ===
+              output
+        @test output == expected
+    end
+    return
+end
+
+function test_Rational_BigInt_mixed_integers()
+    for op in (+, -), (x, y) in ((big(1) // 2, 1 // 3), (big(7) // 6, 5 // 4))
+        expected = op(x, y)
+        @test MA.operate!!(op, deepcopy(x), y) == expected
+        buffer = MA.buffer_for(op, typeof(x), typeof(y))
+        output = zero(x)
+        @test MA.buffered_operate_to!(buffer, output, op, x, y) === output
+        @test output == expected
+    end
+    return
+end
+
 end  # TestBig
 
 TestBig.runtests()