5.13 How to define your own data types?

Use `type/name` to define new type name.

`type/char`:= x-> x::string and length(x)=1; 
 
P:= proc(c::char) print(c) end proc: 
P("x"); 
                           "x" 
P("xy"); 
Error, invalid input: P expects its 1st argument, c, to be of type char, but received xy 
 
> `type/byte`:= x-> x::integer and (x>= 0 and x<256); 
 
#will define a byte (unsigned integer)