'class' or 'typename' for Template Parameters: When to Use Which?

Determining the Choice between 'class' and 'typename' for Template Parameters

In C template definitions, the question arises whether to employ 'class' or 'typename' for template parameters. This article aims to provide a comprehensive understanding of the implications and underlying reasons behind these choices.

Originally, the keyword 'class' was introduced by Stroustrup to specify types in templates, with the intention of avoiding the introduction of a new keyword. However, some committee members expressed concerns about potential confusion due to the overloading of 'class,' as it already denoted a type declaration.

To address this, the committee introduced 'typename' as a new keyword specifically designated for specifying template types. This move aimed to reduce syntactic ambiguity and guide developers toward a more precise and intuitive approach. However, 'class' retained its previous functionality to ensure backward compatibility.

As a result, both 'class' and 'typename' remain valid options for defining template parameters in C , serving as interchangeable keywords. Some developers may prefer 'typename' to avoid confusion, while others may maintain tradition and stick with 'class.' Ultimately, the choice between 'class' and 'typename' is a matter of personal preference, with no significant technical implications.

It is worth noting that before C 17, 'class' was a requirement for template template parameters. However, with the introduction of C 17, 'typename' became the preferred option also in this context, aligning with a more coherent syntax for template types.

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