What does this symbol mean <:a> Thank you!

[LuccaT95]

I wish to answer a community question raised by Learn Tau. The question is what the symbol <:a> means.

In short <:a> is an uninterpreted constant in the Tau language. Our general syntax for such a constant is <name1:name2> where name1 and name2 are just strings starting with a letter.
An uninterpreted constant can be best thought of as an (from the outside of the formula) existentially quantified variable. However, if you run a Tau specification that contains uninterpreted constants, prior to execution they are assigned a default value and in this regard they behave different from quantified variables.

Some more information can also be found in the README: https://github.com/IDNI/tau-lang?tab=readme-ov-file#uninterpreted-constants.

All the best,
Lucca

[LEARNTAU]

Thank you Lucca for your response.