A sequence of put-back terminal symbols, terminal symbol placeholders, and terminal symbol classes is such a sequence followed by ‘~’. While processing the sequence, a parser does not consume corresponding terminal symbols from a parse unit or training terminal symbol sequence.
Example
(before reading the sequence)
The sequence of put-back terminal symbols and terminal symbol placeholders in a grammar:
"a" . . . .~The remaining part of training terminal symbol sequence:
a b c d e f g h(after reading the sequence)
The read instance of the sequence:
"a" "b" "c" "d" "e"~The remaining part of training terminal symbol sequence:
a b c d e f g h
Note: in a bottom-up template grammar, the notation ‘"a" . . . .~’ means that the terminal symbol sequence ‘"a" . . .’ is the input one, and only the last terminal symbol placeholder
.~is the put-back one.