MacOS – How to install a specific version of OCaml on MacOS

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I am trying to install version 4.02.3 of OCaml on MacOS 10.14.6 with the following command

brew install ocaml@4.02.3

but I get an error

Error: No available formula with the name "ocaml@4.02.3"

I need that specific version to compile unison with that specific version, so I can use unison between a Linux box (where I cannot install a different version of ocaml and the Mac).

Best Answer

You can use the git history to obtain the formula for OCaml 4.02.3

Go to the local directory where formulas are stored:

cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula

Look at the history of the OCaml formula:

git log ocaml.rb

It appears that the last commit of version 4.02.3 is commit 3cdad82334496ca9fe8d8fb37.

Check out this commit:

git checkout 3cdad82334496ca9fe8d8fb37

By default, Homebrew make an update before an install, so you have to specify to not update before the install:

HOMEBREW_NO_AUTO_UPDATE=1 brew install ocaml

Check that you have the right version with:

ocaml -version

When finished, don't forget to go back to the master branch, in the /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula directory:

git checkout master
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