Download presentation
Presentation is loading. Please wait.
Published byMadison Wilson Modified over 8 years ago
1
7.2 Programming Languages - An Introduction to Informatics - 2008. 11. 17 WMN Lab. Hye-Jin Lee
2
outline Grammar of Languages Syntax and Semantics Backus-Naur Form BNF Definition
3
Grammar of Languages languages a set of sentences sentence subject predicate subject predicate conjunctive sentence subject noun | pronoun predicate verb | verb prepositional-phrase noun MARY | SCHOOL | TOWN pronoun HE verb DRIVES | WALKS | GOES prepositional-phrase preposition noun preposition TO | FROM e.g., {HE, MARY,DRIVES, WALKS, GOES, TO, FROM, TOWN, SCHOOL}
4
Grammar of Languages HE DRIVES FROMS SHOOL pronoun verb preposition noun prepositional-phrase subject predicate sentence Figure 7-7 (a) Simple Sentence
5
Syntax and Semantics The Syntax of a language is given by a set of composition rules called a grammar that defines the elements and structure of any well-formed sentence. The Semantics depends on both the particular words in the sentence and the structure of the sentence. syntax semantics programming language
6
Backus-Naur Form John Backus and Peter Naur developed a formal notation for specifying programming language syntax (in 1959/1960) –Defines the language sentence generated production rule. –Production rule Left side – defined target Right side – representation for the target definition.
7
BNF Definition For example ::= | ::= + | − ::= | ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 Notational convention –Nonterminal symbols is distinguished by enclosing them by brackets “ ”. –::= “is defined as”, “generates”, “produces”, “may be rewritten as”, and “consists of”. –Elements of the vocabulary, sometimes called terminal symbols, appear only in the right parts of rules. –| “or”
8
BNF Definition − 3 6 9 Figure 7-8 parse of an Integer
9
BNF Definition A grammar should be designed not only to produce the correct sentences of the language but also to have syntactic categories that correspond to the semantics of the language. For example – A + B X C + (E − F) ::= | | ::= | ::= | | ( ) ::= + | - ::= x | / ::= | ::= 0|1|2|3|4|5|6|7|8|9 ::= | | ::= A|B| … | Z
10
BNF Definition ( ( ) ( ) ) ( ) Fiqure 7-9 : Parse of a Parenthesis String A + B x C + ( E - F ) l ao l mo l ao l ao l v v v v v f f f f f t t e t e e e f t e
11
Syntax Charts Visual expression of the grammar –Terminals –Non-Terminals –Optional –Zero-Or-More Repititions + number
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.