A note on Flat Assembler's macro capabilities

One of the huge advantages of Flat Assemblers over other assemblers for the Intel platform is its macro engine. In addition to being able to perform its original task--substituting macro instructions with their definitions--it is able to perform relatively complex computations, and I would dare to call it an additional programming language. The preceding examples only utilize a tiny fraction of what FASM's macro processor is capable of. While we only used a set of if clauses and a variable, we may, in necessary cases, use loops (with while or repeat statements). For example, imagine a string of characters that you want to keep encrypted:

my_string  db 'This string will be encrypted',0x0d, 0x0a, 0x00
my_string_len = $ - my_string

Here, my_string_len is the length of the string.

Note

$ is a special symbol denoting the current address. Thus, $-my_string means the current address minus the address of my_string, which is the length of the string.

A simplistic...