A bottom-up parse corresponds to the construction of a parse tree for an input string beginning at the leaves (the bottom) and working up towards the root (the top) . It is convenient to describe parsing as the process of building parse trees, although a front end may in fact carry out a translation directly without building an explicit tree.

We can think of bottom-up parsing as the process of reducing a string w to the start symbol of the grammar. At each reduction step, a specific substring matching the body of a production is replaced by the non terminal at the head of that production. The key decisions during bottom-up parsing are about when to reduce and about what production to apply, as the parse proceeds.

-A bottom-up parse corresponds to the construction of a parse tree for an input string beginning at the leaves (the bottom) and working up towards the root (the top) . It is convenient to describe parsing as the process of building parse trees, although a front end may in fact carry out a translation directly without building an explicit tree.

We can think of bottom-up parsing as the process of　reducing　a string w to the start symbol of the grammar. At each reduction step, a specific substring matching the body of a production is replaced by the non terminal at the head of that production. The key decisions during bottom-up parsing are about when to reduce and about what production to apply, as the parse proceeds.