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Enforced ES.23 upon example code: Introduction and Philosophy #1577

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Enforced ES.23 upon example code: Introduction and Philosophy #1577

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5d51976
Enforced ES.23 upon example code: Introduction and Philosophy
Feb 29, 2020
2f5434a
Reverted erroneous modifications
Mar 20, 2020
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55 changes: 28 additions & 27 deletions CppCoreGuidelines.md
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Original file line number Diff line number Diff line change
Expand Up @@ -503,8 +503,8 @@ This loop is a restricted form of `std::find`:
string val;
cin >> val;
// ...
int index = -1; // bad, plus should use gsl::index
for (int i = 0; i < v.size(); ++i) {
int index{ -1 }; // bad, plus should use gsl::index
for (int i{ 0 }; i < v.size(); ++i) {
if (v[i] == val) {
index = i;
break;
Expand Down Expand Up @@ -596,7 +596,7 @@ Unless the intent of some code is stated (e.g., in names or comments), it is imp

##### Example

gsl::index i = 0;
gsl::index i{ 0 };
while (i < v.size()) {
// ... do something with v[i] ...
}
Expand Down Expand Up @@ -692,8 +692,8 @@ You don't need to write error handlers for errors caught at compile time.
##### Example

// Int is an alias used for integers
int bits = 0; // don't: avoidable code
for (Int i = 1; i; i <<= 1)
int bits{ 0 }; // don't: avoidable code
for (Int i{ 1 }; i; i <<= 1)
++bits;
if (bits < 32)
cerr << "Int too small\n";
Expand Down Expand Up @@ -792,7 +792,7 @@ We need to pass the pointer and the number of elements as an integral object:
{
vector<int> v(n);
f4(v); // pass a reference, retain ownership
f4(span<int>{v}); // pass a view, retain ownership
f4(span<int>{ v }); // pass a view, retain ownership
}

This design carries the number of elements along as an integral part of an object, so that errors are unlikely and dynamic (run-time) checking is always feasible, if not always affordable.
Expand Down Expand Up @@ -844,12 +844,12 @@ Avoid errors leading to (possibly unrecognized) wrong results.

void increment1(int* p, int n) // bad: error-prone
{
for (int i = 0; i < n; ++i) ++p[i];
for (int i{ 0 }; i < n; ++i) ++p[i];
}

void use1(int m)
{
const int n = 10;
const int n{ 10 };
int a[n] = {};
// ...
increment1(a, m); // maybe typo, maybe m <= n is supposed
Expand All @@ -869,10 +869,10 @@ We could check earlier and improve the code:

void use2(int m)
{
const int n = 10;
const int n{ 10 };
int a[n] = {};
// ...
increment2({a, m}); // maybe typo, maybe m <= n is supposed
increment2({ a, m }); // maybe typo, maybe m <= n is supposed
// ...
}

Expand All @@ -881,7 +881,7 @@ If all we had was a typo so that we meant to use `n` as the bound, the code coul

void use3(int m)
{
const int n = 10;
const int n{ 10 };
int a[n] = {};
// ...
increment2(a); // the number of elements of a need not be repeated
Expand All @@ -904,7 +904,7 @@ Don't repeatedly check the same value. Don't pass structured data as strings:

void user2()
{
Date d = read_date(cin);
Date d{ read_date(cin) };
// ...
user1(d.to_string());
// ...
Expand All @@ -922,9 +922,10 @@ There are cases where checking early is dumb because you may not ever need the v
float y;
float z;
float e;

public:
Jet(float x, float y, float z, float e)
:x(x), y(y), z(z), e(e)
:x{ x }, y{ y }, z{ z }, e{ e }
{
// Should I check here that the values are physically meaningful?
}
Expand Down Expand Up @@ -961,7 +962,7 @@ This is particularly important for long-running programs, but is an essential pi

void f(char* name)
{
FILE* input = fopen(name, "r");
FILE* input{ fopen(name, "r") };
// ...
if (something) return; // bad: if something == true, a file handle is leaked
// ...
Expand All @@ -972,7 +973,7 @@ Prefer [RAII](#Rr-raii):

void f(char* name)
{
ifstream input {name};
ifstream input{ name };
// ...
if (something) return; // OK: no leak
// ...
Expand Down Expand Up @@ -1022,29 +1023,29 @@ Time and space that you spend well to achieve a goal (e.g., speed of development
string s;
char ch2;

X& operator=(const X& a);
X& operator =(const X& a);
X(const X&);
};

X waste(const char* p)
{
if (!p) throw Nullptr_error{};
int n = strlen(p);
auto buf = new char[n];
int n{ strlen(p) };
auto buf{ new char[n] };
if (!buf) throw Allocation_error{};
for (int i = 0; i < n; ++i) buf[i] = p[i];
for (int i{ 0 }; i < n; ++i) buf[i] = p[i];
// ... manipulate buffer ...
X x;
x.ch = 'a';
x.s = string(n); // give x.s space for *p
for (gsl::index i = 0; i < x.s.size(); ++i) x.s[i] = buf[i]; // copy buf into x.s
for (gsl::index i{ 0 }; i < x.s.size(); ++i) x.s[i] = buf[i]; // copy buf into x.s
delete[] buf;
return x;
}

void driver()
{
X x = waste("Typical argument");
X x{ waste("Typical argument") };
// ...
}

Expand All @@ -1059,7 +1060,7 @@ There are several more performance bugs and gratuitous complication.

void lower(zstring s)
{
for (int i = 0; i < strlen(s); ++i) s[i] = tolower(s[i]);
for (int i{ 0 }; i < strlen(s); ++i) s[i] = tolower(s[i]);
}

This is actually an example from production code.
Expand Down Expand Up @@ -1100,9 +1101,9 @@ Messy, low-level code breeds more such code.

##### Example

int sz = 100;
int* p = (int*) malloc(sizeof(int) * sz);
int count = 0;
int sz{ 100 };
int* p{ (int*) malloc(sizeof(int) * sz) };
int count{ 0 };
// ...
for (;;) {
// ... read an int into x, exit loop if end of file is reached ...
Expand Down Expand Up @@ -20519,8 +20520,8 @@ A textbook for beginners and relative novices.

## <a name="SS-vid"></a>RS.video: Videos about "modern C++"

* Bjarne Stroustrup: [C++11 Style](http://channel9.msdn.com/Events/GoingNative/GoingNative-2012/Keynote-Bjarne-Stroustrup-Cpp11-Style). 2012.
* Bjarne Stroustrup: [The Essence of C++: With Examples in C++84, C++98, C++11, and C++14](http://channel9.msdn.com/Events/GoingNative/2013/Opening-Keynote-Bjarne-Stroustrup). 2013
* Bjarne Stroustrup: [C++11 Style](http://channel9.msdn.com/Events/GoingNative/GoingNative-2012/Keynote-Bjarne-Stroustrup-Cpp11-Style). 2012.
* Bjarne Stroustrup: [The Essence of C++: With Examples in C++84, C++98, C++11, and C++14](http://channel9.msdn.com/Events/GoingNative/2013/Opening-Keynote-Bjarne-Stroustrup). 2013
* All the talks from [CppCon '14](https://isocpp.org/blog/2014/11/cppcon-videos-c9)
* Bjarne Stroustrup: [The essence of C++](https://www.youtube.com/watch?v=86xWVb4XIyE) at the University of Edinburgh. 2014.
* Bjarne Stroustrup: [The Evolution of C++ Past, Present and Future](https://www.youtube.com/watch?v=_wzc7a3McOs). CppCon 2016 keynote.
Expand Down