This instruction has the syntax
call NONT, ORD
The instruction calls an assembler routine for parsing a nonterminal symbol NONT.
Execution continues after this instruction on finishing parsing the nonterminal symbol.
The argument ORD is the ordinal number of an AST node for the nonterminal symbol in an AST for a regular expression.
topdown uses that ordinal number to mark a part of this regular expression containing a parse error in a stack trace dumped on executing an
call A, 2
This instruction calls an assembler routine for parsing the nonterminal symbol
The AST node of an occurrence of that nonterminal symbol in a regular expression has ordinal number 2.