Limits

Fixed ceilings. Most of them are large enough that a grammar meets none of them; the small ones are small on purpose, and say so.

The grammar

	limit
actions in one program	65,535
semvar sets	16
scopes	16
positions in one scope	4
arms in one binding-power table	64
items in one character class	65,535
programs linked into one run	64

Sixteen semvar sets is a ceiling, not an oversight: a set is a global thing a whole grammar shares, and a grammar that wants a seventeenth usually wants a scope instead.

Sixteen scopes for the same reason, and it follows from the sets. A scope is a depth counter, and what a depth counter is for is emptying the sets bound to it — a scope with nothing bound to it is refused. So a seventeenth scope could only ever govern a set one of the first sixteen already governs. Declaring one is an error, not a silent truncation.

The run

	limit
variable stack	64 KiB, or 64 MiB if it is allowed to grow
binding-power nesting	128 levels
nesting of one ordered scope	its buffer, 64 bytes by default

Plugins

	limit
shared libraries per run	8
foreign symbols bound	64
length of a foreign name	96 bytes

What is not limited

The input, the AST, a semvar set, and how deep a rule may call itself are all bounded by memory rather than by a constant. An action that recurses without consuming will exhaust the variable stack and be told so.