Slang

The S language is a theoretical programming language proposed by Martin Davids in his book Computability, Complexity and Languages. It is composed by labels, variables, and 4 basic instructions, which are:

• V++;: Increments the variable V
• V--;: Decrements the variable V
• V;: Does nothing
• V?L;: If V is different to 0, goes to label L

Labels are written between brackets and can be one of A, B, C, D, E with a subindex.

There are 3 types of variables:

• X with a subindex, are input variables
• Z with a subindex, are auxiliary variables
• Y is the output variable

This language can be used to prove that there are some natural functions which can't be computed. Which is awesome. For more information, check Github's README. On the other side, a full example of a little program written in Slang is as follows:

        [A1] X1++;
                X1--;
                X1?A1;