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T.26: it is better to define concepts based on the use of pattern terms than simple syntax

Reason (reason)

The definition is more readable and corresponds directly to what a user has to write. Conversions are taken into account. You don't have to remember the names of all the type traits.

This definition is more readable and corresponds directly to what the user must write. Conversion is also taken into account. You don't have to remember all the types of features.

Example (using TS concepts) (example (using TS concept))

You might be tempted to define a concept Equality like this:

You might try to define the Equality concept like this:

Template concept Equality = has_equal & & has_not_equal

Obviously, it would be better and easier just to use the standard EqualityComparable, but-just as an example-if you had to define such a concept, prefer:

Obviously, it's better and easier to just use standard EqualityComparable, but it's just an example, and it's better if you have to define such a concept:

Template concept Equality = requires (T a, T b) {

Bool = = {a = = b}

Bool = = {a! = b}

/ / axiom {! (a = = b) = (a! = b)}

/ / axiom {a = b; = > a = = b} / / = > means "implies"

}

As opposed to defining two meaningless concepts has_equal and has_not_equal just as helpers in the definition of Equality. By "meaningless" we mean that we cannot specify the semantics of has_equal in isolation.

Instead of defining meaningless has_equal and has_not_equal concepts just to help define Equality. What we want to say through the word "meaningless" is that we cannot define the semantics of has_equal independently.

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