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BNF grammer

The following BNF grammer describes a Pascal-like syntax for declarations:
<decl_list> -> <decl> ; <decl_list>
| <decl>
<decl> -> <identifier> : <type>
<type> -> integar
| real
| record <decl_list> end
<identifier> -> a | b | c

Using this grammer, give a parse tree and a leftmost derivation for the following sentence:

a : record b : integer; c : real end

AmigoJack

what is "BNF"? by reading everything up to your last sentence, it really looks like how to declare variables, define records and which datatypes can be used.

summoned that, your last line (after your last sentence) would be a record named "a" which has the two members "b" (datatype integer) and "c" (datatype real). is that what you wanted? otherwise please rephrase your last sentence or tell me what a "parse tree" and a "leftmost derivation" is

<identifier> : <type> (where type is a <decl_list> because its no simple datatype)

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AmigoJack

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shahrine99

ASKER

ok....ya it seems right...i looked at my book and looked at several examples for leftmost derviatives and yours seem similiar to it...but what about parse tree? BNF means Backus-Naur Form...it is a way to describe a language in a mathmatical way..i see that you already visted the link that u sent to me.

cup

BNF = Backus Naur Form

A little history: It is based on Chomsky's grammar rules and was originally used to describe Algol 60.
John Backus is the inventor of Fortran.
Peter Naur - see http://en.wikipedia.org/wiki/Peter_Naur - he prefers BNF to be called Backus Normal Form.