mirror of
https://github.com/isocpp/CppCoreGuidelines.git
synced 2025-12-17 04:44:34 +03:00
moved T.140/T.141 to F.10/F.11 leaving redirects behind (closes #1974)
This commit is contained in:
Sergey Zubkov
@@ -2346,6 +2346,8 @@ Function definition rules:
|
||||
* [F.7: For general use, take `T*` or `T&` arguments rather than smart pointers](#Rf-smart)
|
||||
* [F.8: Prefer pure functions](#Rf-pure)
|
||||
* [F.9: Unused parameters should be unnamed](#Rf-unused)
|
||||
* [F.10: If an operation can be reused, give it a name](#Rf-name)
|
||||
* [F.11: Use an unnamed lambda if you need a simple function object in one place only](#Rf-lambda)
|
||||
|
||||
Parameter passing expression rules:
|
||||
|
||||
@@ -2866,6 +2868,91 @@ For example:
|
||||
|
||||
Flag named unused parameters.
|
||||
|
||||
### <a name="Rf-name"></a>F.10: If an operation can be reused, give it a name
|
||||
|
||||
##### Reason
|
||||
|
||||
Documentation, readability, opportunity for reuse.
|
||||
|
||||
##### Example
|
||||
|
||||
struct Rec {
|
||||
string name;
|
||||
string addr;
|
||||
int id; // unique identifier
|
||||
};
|
||||
|
||||
bool same(const Rec& a, const Rec& b)
|
||||
{
|
||||
return a.id == b.id;
|
||||
}
|
||||
|
||||
vector<Rec*> find_id(const string& name); // find all records for "name"
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[&](Rec& r) {
|
||||
if (r.name.size() != n.size()) return false; // name to compare to is in n
|
||||
for (int i = 0; i < r.name.size(); ++i)
|
||||
if (tolower(r.name[i]) != tolower(n[i])) return false;
|
||||
return true;
|
||||
}
|
||||
);
|
||||
|
||||
There is a useful function lurking here (case insensitive string comparison), as there often is when lambda arguments get large.
|
||||
|
||||
bool compare_insensitive(const string& a, const string& b)
|
||||
{
|
||||
if (a.size() != b.size()) return false;
|
||||
for (int i = 0; i < a.size(); ++i) if (tolower(a[i]) != tolower(b[i])) return false;
|
||||
return true;
|
||||
}
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[&](Rec& r) { compare_insensitive(r.name, n); }
|
||||
);
|
||||
|
||||
Or maybe (if you prefer to avoid the implicit name binding to n):
|
||||
|
||||
auto cmp_to_n = [&n](const string& a) { return compare_insensitive(a, n); };
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[](const Rec& r) { return cmp_to_n(r.name); }
|
||||
);
|
||||
|
||||
##### Note
|
||||
|
||||
whether functions, lambdas, or operators.
|
||||
|
||||
##### Exception
|
||||
|
||||
* Lambdas logically used only locally, such as an argument to `for_each` and similar control flow algorithms.
|
||||
* Lambdas as [initializers](#???)
|
||||
|
||||
##### Enforcement
|
||||
|
||||
* (hard) flag similar lambdas
|
||||
* ???
|
||||
|
||||
### <a name="Rf-lambda"></a>F.11: Use an unnamed lambda if you need a simple function object in one place only
|
||||
|
||||
##### Reason
|
||||
|
||||
That makes the code concise and gives better locality than alternatives.
|
||||
|
||||
##### Example
|
||||
|
||||
auto earlyUsersEnd = std::remove_if(users.begin(), users.end(),
|
||||
[](const User &a) { return a.id > 100; });
|
||||
|
||||
|
||||
##### Exception
|
||||
|
||||
Naming a lambda can be useful for clarity even if it is used only once.
|
||||
|
||||
##### Enforcement
|
||||
|
||||
* Look for identical and near identical lambdas (to be replaced with named functions or named lambdas).
|
||||
|
||||
## <a name="SS-call"></a>F.call: Parameter passing
|
||||
|
||||
There are a variety of ways to pass parameters to a function and to return values.
|
||||
@@ -6973,6 +7060,8 @@ Function objects should be cheap to copy (and therefore [passed by value](#Rf-in
|
||||
|
||||
Summary:
|
||||
|
||||
* [F.10: If an operation can be reused, give it a name](#Rf-name)
|
||||
* [F.11: Use an unnamed lambda if you need a simple function object in one place only](#Rf-lambda)
|
||||
* [F.50: Use a lambda when a function won't do (to capture local variables, or to write a local function)](#Rf-capture-vs-overload)
|
||||
* [F.52: Prefer capturing by reference in lambdas that will be used locally, including passed to algorithms](#Rf-reference-capture)
|
||||
* [F.53: Avoid capturing by reference in lambdas that will be used non-locally, including returned, stored on the heap, or passed to another thread](#Rf-value-capture)
|
||||
@@ -16939,7 +17028,7 @@ Metaprogramming rule summary:
|
||||
|
||||
Other template rules summary:
|
||||
|
||||
* [T.140: Name all operations with potential for reuse](#Rt-name)
|
||||
* [T.140: If an operation can be reused, give it a name](#Rt-name)
|
||||
* [T.141: Use an unnamed lambda if you need a simple function object in one place only](#Rt-lambda)
|
||||
* [T.142: Use template variables to simplify notation](#Rt-var)
|
||||
* [T.143: Don't write unintentionally non-generic code](#Rt-non-generic)
|
||||
@@ -18795,90 +18884,13 @@ Write your own "advanced TMP support" only if you really have to.
|
||||
|
||||
## <a name="SS-temp-other"></a>Other template rules
|
||||
|
||||
### <a name="Rt-name"></a>T.140: Name all operations with potential for reuse
|
||||
### <a name="Rt-name"></a>T.140: If an operation can be reused, give it a name](#Rt-name
|
||||
|
||||
##### Reason
|
||||
|
||||
Documentation, readability, opportunity for reuse.
|
||||
|
||||
##### Example
|
||||
|
||||
struct Rec {
|
||||
string name;
|
||||
string addr;
|
||||
int id; // unique identifier
|
||||
};
|
||||
|
||||
bool same(const Rec& a, const Rec& b)
|
||||
{
|
||||
return a.id == b.id;
|
||||
}
|
||||
|
||||
vector<Rec*> find_id(const string& name); // find all records for "name"
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[&](Rec& r) {
|
||||
if (r.name.size() != n.size()) return false; // name to compare to is in n
|
||||
for (int i = 0; i < r.name.size(); ++i)
|
||||
if (tolower(r.name[i]) != tolower(n[i])) return false;
|
||||
return true;
|
||||
}
|
||||
);
|
||||
|
||||
There is a useful function lurking here (case insensitive string comparison), as there often is when lambda arguments get large.
|
||||
|
||||
bool compare_insensitive(const string& a, const string& b)
|
||||
{
|
||||
if (a.size() != b.size()) return false;
|
||||
for (int i = 0; i < a.size(); ++i) if (tolower(a[i]) != tolower(b[i])) return false;
|
||||
return true;
|
||||
}
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[&](Rec& r) { compare_insensitive(r.name, n); }
|
||||
);
|
||||
|
||||
Or maybe (if you prefer to avoid the implicit name binding to n):
|
||||
|
||||
auto cmp_to_n = [&n](const string& a) { return compare_insensitive(a, n); };
|
||||
|
||||
auto x = find_if(vr.begin(), vr.end(),
|
||||
[](const Rec& r) { return cmp_to_n(r.name); }
|
||||
);
|
||||
|
||||
##### Note
|
||||
|
||||
whether functions, lambdas, or operators.
|
||||
|
||||
##### Exception
|
||||
|
||||
* Lambdas logically used only locally, such as an argument to `for_each` and similar control flow algorithms.
|
||||
* Lambdas as [initializers](#???)
|
||||
|
||||
##### Enforcement
|
||||
|
||||
* (hard) flag similar lambdas
|
||||
* ???
|
||||
See [F.10](#Rf-name)
|
||||
|
||||
### <a name="Rt-lambda"></a>T.141: Use an unnamed lambda if you need a simple function object in one place only
|
||||
|
||||
##### Reason
|
||||
|
||||
That makes the code concise and gives better locality than alternatives.
|
||||
|
||||
##### Example
|
||||
|
||||
auto earlyUsersEnd = std::remove_if(users.begin(), users.end(),
|
||||
[](const User &a) { return a.id > 100; });
|
||||
|
||||
|
||||
##### Exception
|
||||
|
||||
Naming a lambda can be useful for clarity even if it is used only once.
|
||||
|
||||
##### Enforcement
|
||||
|
||||
* Look for identical and near identical lambdas (to be replaced with named functions or named lambdas).
|
||||
See [F.11](#Rf-lambda)
|
||||
|
||||
### <a name="Rt-var"></a>T.142?: Use template variables to simplify notation
|
||||
|
||||
|
||||
Reference in New Issue
Block a user