End of a token sas-end-of-token
The word scanner recognizes the end of a token by a white space, the two macro triggers (%, &), by the dot (.) or by a special token (+, ; …).
Macro triggers
If the word scanner fetches a macro trigger (% or &), it does not push the next token to the word queue.
Rather, it invokes the (multi-component)
macro processor to process them further.
The macro processor might push text into the
input stack.
For example, if the condition of an
%if statement is met, the corresponding text is pushed back.
Similarly, a
%do statement might push text multiple times to the input stack.