Lead and last in compiler design

lead

• 1st element in RHS of production and the accompanying non-terminal(where non-terminal  end in terminal that symbol)
• X-a
• X-sH
• H-e
• here lead of X: a,s,e.
• we only write terminal in lead of grammer.
• here H was non terminal so its end terminal was taken

last

• last element in RHS of production and the following non-terminal(where it end in terminal that symbol)
• X-.....a
• X-......sH
• H-.....e
• here last of X: a,s,e.
• we only write terminal in last of  grammar.