I tried to install it via brew and it worked without issues. Is this still an issue for you?
It's not, after you explained I should not use gcc-9 compiler on OS X. I have no problems building with gcc-8 on linux boxes and clang 11 on OS X. Build
Souffle: 1.7.1-1303-g45a8fdc1 on OS X works for me as well, thanks for your support.
One last question: what's the exact difference between
.type Distance <: number
.type Distance = number
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