ecl_concepts Documentation

ecl_concepts

Introduces a compile time concept checking mechanism that can be used most commonly to check for required functionality when passing template arguments.

Embedded Control Library

One of the problem with template usage occurs occurs in the following scenario. For templatised functions and classes, the input template arguments usually have little or no restriction on the class that can be used, e.g.

template <typename T>
void f(T input) {
// use some aspect of T's interface
}

Of course the compile will fail if you try to use an input type, T, that doesn't have the specialised interface you want, but the compile time error message is often very verbose and its difficult to find the error. An idea which is merging into the c++ mainstream as well as that used by the boost concept checking library is to characterise common behaviours into Concepts. A simplified version of this is utilised here.

Compiling & Linking

Include the following at the top of any translation unit that requires compilation of signals and/or slots.

Since it is a collection of macros and template functions/classes, no linking is required if you are only utilising this functionality.

Usage

Usage is fairly simple. There are two steps:

Concept Test

If you are using an existing concept (see below), skip through to the concept check. Otherwise:

The example here is the same as that used in src/tests/concepts.cpp:

template <typename T>
class MyConcept {
public:
compile_time_concept_test(MyConcept) {
T t;
t.apply(); // This is the characteristic function required by this concept.
}
};

Hand-crafting the concept testing function will often require a little care to ensure the concept is appropriately covered.

Concept Check

Once you have a test in place, you only need to insert compile_time_concept_check() calls wherever you need them. Keep in mind, the sole purpose of these is to provide convenient error logs when something goes wrong.

class A { // This class has the MyConcept functionality.
public:
// The following function characterises the MyConcept concept.
// Comment this line and any MyConcept concept assertion
// check will fail in compile time.
void apply() {};
};
int main() {
compile_time_concept_check(MyConcept<A>); // Checks A for compliance to the MyConcept concept.
return 0;
}

Existing Concepts

Examples

ChangeLog

    - @ref changelogConcepts "ChangeLog"


ecl_concepts
Author(s): Daniel Stonier
autogenerated on Thu Jun 6 2019 21:58:35