ScalarExpression concept

Description

A scalar expression is an expression which after computation results in a scalar. Thus a scalar expression can be assigned to a scalar (relying on a conversion if necessary).

Refinement of

Expression.

Associated types

Those of Expression.

Notation

`X`	Type that is a model of ScalarExpression
`C`	Type so that `X` is convertible to `C`
`a`	Objects of type `X`
`c`	Object of type `C`

Definitions

Valid expressions

In addition to those of Expression:

Name	Expression	Type requirements	Return type
ConversionAssignment	`c=a`		`C`
ConversionConstructor	`C c(a)`		`C`

ScalarExpression semantics

In addition to those of Expression:

Name	Expression	Precondition	Semantics	Postcondition
ConversionAssignment [1]	`c=a`		Returns the value of the expression
ConversionConstructor [1]	`C c(a)`		Returns the value of the expression

Complexity guarantees

Invariants

Models

Notes

[1] Generally any scalar-expression will have to implement a templated conversion operator ('template <class T> T operator() const') to allow this conversion. Scalars are different in respect to vector and matrices because it is not possible to add an assignment operator to the builtin types (scalars) that accept a scalar-expression. One can argue that it is neither possible to add an assignment operator to std::vector and thus an implicit conversion operator should be foreseen for vector-expressions too. The drawback however would be that this would be very inefficient for vectors to return them by value and thus an assign is thus far superior anyway.