Now that homebrew/versions has been deprecated, homebrew/core supports multiple versions of formulae with a new naming format.

In homebrew/versions the formula for GCC 6 was named gcc6.rb and began with class Gcc6 < Formula. In homebrew/core this same formula is named gcc@6.rb and begins with class GccAT6 < Formula.

Acceptable versioned formulae

Versioned formulae we include in homebrew/core must meet the following standards:

Homebrew’s versions are not intended to be used for any old versions you personally require for your project. You should create your own tap for formulae you or your organisation wish to control the versioning of or those that do not meet the above standards. Software that has regular API or ABI breaking releases still needs to meet all the above requirements; that a brew upgrade has broken something for you is not an argument for us to add and maintain a formula for you.

We may temporarily add versioned formulae for our own needs that do not meet these standards in homebrew/core. The presence of a versioned formula there does not imply it will be maintained indefinitely or that we are willing to accept any more versions that do not meet the requirements above.

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