This program is a symbolic unifier meant to unify two expressions into one
expression if possible. If the unification isn't possible then the program will
output why it wasn't possible to stderr and fail. Otherwise, the program will
output the unified expression on stdout and return successfully.
Simply clone the repository and run make in the directory to compile the
program. There's no dependencies and was written conforming to C++98.
The program accepts a string of characters on stdin or as the first argument
and parses them. The program accepts single expressions, e.g. f(?x), and will
output them without error. To unify two expressions assert them with =, e.g.
f(?x) = f(5). That will return f(5).
Variables are defined as any constant prefixed with a ?. A variable function
isn't allowed, e.g. ?x(). Constants are any value that's not a function,
e.g. 5 or a. And a function is just a name with parenthesis wrapping
arguments, e.g. f(?x), g(?y, f(?z)), h().
Don't forget to give the entire expression as a string, e.g. ./unify "f(?x)".
I needed this unifier for a larger project. I also really wanted to build a parser for a somewhat mathematical language.
I really enjoyed how the specific data isn't parsed for anything other than a
pointer value. For the expression f(?x, 5) = f(?y, ?x) the values f,
?x, ?y and 5 all have a different pointer values, but they are chained so
that ?y becomes the value of ?x and ?x becomes 5. There's no parsing
for explicit data types like integers. Simply test for equality with pointers.