This instruction has the syntax
The instruction analyzes a look-ahead symbol from a training terminal symbol sequence and returns an outcome equal to the numeric identifier of this look-ahead terminal symbol.
The argument ORD is the ordinal number of an AST node for a ‘?’ or ‘*’ quantifier or a set of alternatives separated by ‘|’ requiring look-ahead terminal symbol analysis to select a branch for transferring control.
topdown uses that ordinal number to mark a regular expression part containing a parse error in a stack trace dumped on executing an
This instruction returns the identifier of the next terminal symbol from a training terminal symbol sequence to select a control transfer target for an AST node with ordinal number 3.