Install icu4c version 64 with Homebrew

download the homebrew core first 

git clone https://github.com/Homebrew/homebrew-core.git
 

check current installed version 

brew list --versions icu4c

 

1) cd to Homebrew's formula directory

cd $(brew --prefix)/Homebrew/Library/Taps/homebrew/homebrew-core/Formula

2) Find desired commit (version 63 for icu4c) to checkout

git log --follow icu4c.rb

3) Checkout to a new branch

git checkout -b icu4c-64 896d1018c7a4906f2c3fa1386aaf283497db60a2

4) Reinstall the library with the new version

brew reinstall ./icu4c.rb

5) Switch to the reinstalled version

brew switch icu4c 64.2

6) Checkout back to master

git checkout master

 

 

references 

- https://github.com/eXolnet/homebrew-deprecated/issues/27

- https://stackoverflow.com/questions/55826221/install-icu4c-version-63-with-homebrew