[metapost] Maximum length of a text argument

[Nicola]

Hi,
I am writing some macros that take potentially long text arguments, e.g.,

def eat text food =
  % Do something with food
enddef;

eat begingroup
  % Very long list of instructions
endgroup;

What is, approximately, the maximum length of such an argument? I have tried a 
quick test, and I found that the above macro can... eat ~1MB of tokens (which 
for me would me more than enough), but my test may be flawed. Is that really the 
case?

Nicola