Empty string Analogous to the empty set in set theory, the empty string is a character string of length zero. As input to the machine is processed, the machine moves from state to state as specified by the logic of the machine. In the case of the parser, the input is the language being parsed, and the states correspond to various stages in the grammar rules. Infix operator An arithmetic operator that is placed between the operands on which it performs some operation. A continuous flow of data between devices or programs.
Language construct One of the typical usage schemas of the language.
Language and Grammar . A function that reads an input stream and returns tokens one by one. Lexical tie-in A flag, set by actions in the grammar rules, which alters the way tokens are parsed. See Lexical Tie-ins . Look-ahead token A token already read but not yet shifted.