SLR generators calculate that lookahead by an easy approximation method based directly on the grammar, ignoring the details of individual parser states and transitions. This ignores the particular context of the current parser state. If some nonterminal symbol "S" is used in several places in the grammar, SLR treats those places in the same single way rather than handling them individually. The SLR generator works out codice_1, the set of all terminal symbols which can immediately follow some occurrence of "S". In the parse table, each reduction to "S" uses Follow(S) as its LR(1) lookahead set. Such follow sets are also used by generators for LL top-down parsers. A grammar that has no shift/reduce or reduce/reduce conflicts when using follow sets is called an SLR grammar.