[metapost] Using |s| as a variable name

[Taco Hoekwater]

nicola wrote:
> and why does the following produce an error?
> 
>    string s;
>    s = "aaaaaaa";
>    |s| = length s;
>    for i = 1 upto |s|:
>       ;
>    endfor;

Because the colon is taken to be part of the variable name,
as it is in the same character class as the pipe symbol.

This works:

   for i = 1 upto |s| :

and so does this:

   for i = 1 upto (|s|):

Best wishes,
Taco