From c2ec583c30cc95dd681dbb0c9fc5a46572913e22 Mon Sep 17 00:00:00 2001
From: Nao Pross <naopross@thearcway.org>
Date: Mon, 10 Dec 2018 15:10:55 +0100
Subject: Update makefile ad update basic_vec to allow abstract algebraic
 structures

Unfortunately this requires C++17 as `static constexpr` members
have an undefined behaviour before this version.
---
 vector/makefile   |  4 ++--
 vector/vector.cpp | 13 +++++++++----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/vector/makefile b/vector/makefile
index 1303aa3..31136ea 100644
--- a/vector/makefile
+++ b/vector/makefile
@@ -2,8 +2,8 @@ CC      := gcc
 CARGS   := -Wall -Werror -I.
 LDARGS  := -lm
 
-CPPC    := g++
-CPPARGS := -Wall -I.
+CPPC    := g++-8
+CPPARGS := -Wall -I. -std=c++17
 
 all: vector.pdf c_build/vector cpp_build/vector
 
diff --git a/vector/vector.cpp b/vector/vector.cpp
index 9e0ca6c..d5f0c36 100644
--- a/vector/vector.cpp
+++ b/vector/vector.cpp
@@ -6,10 +6,15 @@
 #include <initializer_list>
 #include <algorithm>
 
+
 template<typename T, std::size_t d>
 struct basic_vec : public std::array<T, d> {
     static constexpr std::size_t dimensions = d;
 
+    static constexpr T null_element = static_cast<T>(0);
+    static constexpr T unit_element = static_cast<T>(1);
+    static constexpr T unit_additive_inverse_element = static_cast<T>(-1);
+
     basic_vec();
     basic_vec(const std::initializer_list<T> l);
     template<std::size_t n> basic_vec(const basic_vec<T, n>& other);
@@ -19,7 +24,7 @@ struct basic_vec : public std::array<T, d> {
 
 template<typename T, std::size_t d>
 basic_vec<T, d>::basic_vec() : std::array<T, d>() {
-    this->fill(static_cast<T>(0));
+    this->fill(basic_vec<T,d>::null_element);
 }
 
 template<typename T, std::size_t d>
@@ -44,7 +49,7 @@ basic_vec<T, d>::basic_vec(const basic_vec<T, n>& other) {
 
 template<typename T, std::size_t d>
 T basic_vec<T, d>::length() const {
-    T res = static_cast<T>(0);
+    T res = basic_vec<T, d>::null_element;
     for (const T& val : *this) {
         res += val * val;
     }
@@ -77,12 +82,12 @@ basic_vec<T, d> operator*(const T& rhs, const basic_vec<T, d>& lhs) {
 
 template<typename T, std::size_t d>
 basic_vec<T, d> operator-(const basic_vec<T, d>& rhs, const basic_vec<T, d>& lhs) {
-    return rhs + static_cast<T>(-1) * lhs;
+    return rhs + basic_vec<T, d>::unit_additive_inverse_element * lhs;
 }
 
 template<typename T, std::size_t d>
 T operator*(const basic_vec<T, d>& rhs, const basic_vec<T, d>& lhs) {
-    T res = static_cast<T>(0);
+    T res = basic_vec<T, d>::null_element;
     for (std::size_t i = 0; i < d; i++) {
         res += rhs[i] * lhs[i];
     }
-- 
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