auto reduction of phi-expressions

[yegor256]

There are expressions in phi-calculus, for example this one:

[ y -> [ z -> 42 ].z ].y

It may be reduced to:

[ z -> 42 ].z

And then to:

42

There is a dozen of reduction rules, which are well defined. We should implement a program, which will take an expression as an input and then show step by step how it is reduced to a normal form (when no rules can be applied any more). The output of the program should be a list of expressions, starting from the incoming expression till the normal form.

I suggest we implement this in Coq.

[l3r8yJ]

@yegor256 can i take it? If so, how should I start it, just create a new repo, then move it to Objectionary?