The macro language is a character-based language. Even variables that appear to be numeric are generally treated as character variables (except during expression evaluation). Therefore, the macro ...

I've read this blog post: Macros: why they're evil., and it really illuminated for me Metasyntactic's point of view in his several discussions with Rayiner about macros. I didn't get Meta's idea ...

When the macro processor executes a macro program statement that can create a macro variable (such as a %LET statement), the macro processor attempts to change the value of an existing macro variable ...