Operator precedence

Question

EF→E∗F∣F+E∣F→F−F∣id

E -> E*F | F+E | F

F -> F - F | id

What is operator precedence order for * , + , - ?

Answer 1

In your 1st line you have written  EF→E∗F  ..  EF !!   typing error? If it is edit it.

Next . coming to whatever you have written in big fonts.

E -> E*F | F+E | F

F -> F - F | id

* & + are at same level so their precedence is same.
' - ' has more precedence than * & +  because it is more close to leaf in parse tree...

Rule is simple. The operator more close to leaf will be evaluated first so it has highest precedence, operator at root has least precedence. If they are in same level, they have same precedence.

Comments

This rule is valid for ambiguous grammar as we right ?

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This rule is for any grammar... precedence depends on the height of operator in parse tree.

Answer 2

- is having higher precedence than both * and +.

The highest precedence operator is placed farther from the start symbol of the CFG as it has to be evaluated first.

* and + have the same precedence as they are at the same level.