From da8b08e4e3d7c189c11b1db6abf10926ba8373f7 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Tue, 12 Oct 2021 15:02:33 +0200
Subject: [PATCH 1/3] abacus: bignum: use IIFE

I think it looks cleaner to use Immediately Invoked Function Expressions
in such cases.
---
 src/bignum/bignum.cc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/bignum/bignum.cc b/src/bignum/bignum.cc
index 2121cdc..6b6987e 100644
--- a/src/bignum/bignum.cc
+++ b/src/bignum/bignum.cc
@@ -82,12 +82,12 @@ digits_type do_addition(digits_type const& lhs, digits_type const& rhs) {
         ++it2;
     }
 
-    auto it = it1;
-    auto end = end1;
-    if (it1 == end1) {
-        it = it2;
-        end = end2;
-    }
+    auto [it, end] = [=]() {
+        if (it1 != end1) {
+            return std::make_pair(it1, end1);
+        }
+        return std::make_pair(it2, end2);
+    }();
 
     while (it != end) {
         int addition = *it + carry;

From 4ea7a38b614fdef27423a340c85459ce151fdf70 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Tue, 12 Oct 2021 15:05:38 +0200
Subject: [PATCH 2/3] abacus: use C++20

---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d343e5a..7d72bf3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ enable_testing()
 
 add_library(common_options INTERFACE)
 target_compile_features(common_options INTERFACE
-  cxx_std_17
+  cxx_std_20
 )
 target_compile_options(common_options INTERFACE
   -Wall

From 8cb26ee31611287cc32d8cf042bac47198e5c5f0 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Tue, 12 Oct 2021 15:05:21 +0200
Subject: [PATCH 3/3] abacus: bignum: use span

Once again, the code looks cleaner that way.
---
 src/bignum/bignum.cc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/bignum/bignum.cc b/src/bignum/bignum.cc
index 6b6987e..cadc170 100644
--- a/src/bignum/bignum.cc
+++ b/src/bignum/bignum.cc
@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <iostream>
 #include <iterator>
+#include <span>
 
 #include <cassert>
 #include <cmath>
@@ -82,18 +83,17 @@ digits_type do_addition(digits_type const& lhs, digits_type const& rhs) {
         ++it2;
     }
 
-    auto [it, end] = [=]() {
+    auto leftover = [=]() {
         if (it1 != end1) {
-            return std::make_pair(it1, end1);
+            return std::span(it1, end1);
         }
-        return std::make_pair(it2, end2);
+        return std::span(it2, end2);
     }();
 
-    while (it != end) {
-        int addition = *it + carry;
+    for (auto value : leftover) {
+        int addition = value + carry;
         carry = addition / BASE;
         res.push_back(addition % BASE);
-        ++it;
     }
 
     if (carry != 0) {