A poor man's Option types in C.

See example code for usage.

Operations:

• OPTION(type): the signature for options of a given base type type
• NONE: empty constructor
• JUST: non-empty constructor
• IS_NONE: checks whether the option type is empty
• IS_JUST: checks whether the option type is non-empty
• UNWRAP: unwraps the option type after asserting it is non-empty
• UNWRAP_OR: unwraps the option type if present, else returns the default
• EQ: compares two options using ==; none matches none
• EQUAL: compares two options using ==; none does not match none
• OR: return the first option if present, else the second
• AND: return the first option if not present, else the second
• IF_LET: unwrap the option if present and execute a block
• IF_NOT: execute a block if the option is not present