Compiler Design

1. Compilers Design
Course
Ramadan Babers
Compilers Design – Lec5
Faculty of Science Helwan University
1st Term – 2017/2018

2. 2
Chapter 2
A Simple Syntax-Directed
Translator

3. 2.3.1 Postfix
3
Infix Postfix
5+2
(5+2)
1+2-3
1+2*3
1+2*(3+5)
1+2*3*(4+5)-6*7
52+
52+ (there is no () in postfix)
12+3-
123*+
1+X
1X+ ….. X=2L* ….. L=35+
1235+*+
1+X-Y
1X+Y- ….. X=23*Z* … Z=45+ ….. Y=67*
123*45+*+67*-

4. 4
Example: 5-(2*1)+1
Syntax-directed definition for infix to postfix translation
Productions Semantic Rules (Postfix)
expr expr + term
expr expr – term
expr term
term term * f
term term / f
term f
f (expr)
f digit
digit 0
digit 1
digit 9
expr.t = expr .t || term.t || ‘+’
expr.t = expr .t || term.t || ‘-’
expr.t = term.t
term.t = term.t || f.t || ‘*’
term.t = term.t || f.t || ‘/’
term.t = f.t
f.t = (expr.t)
f.t = digit.t
digit.t = ‘0’
digit.t = ‘1’
digit.t = ‘9’
1
1
1
1

5. 5

6. 6
2.3.5 Translation Schemes
Actions for translating into postfix notation
expr expr + term {print (‘+’)}
expr expr – term {print (‘-’)}
expr term
term term * f {print (‘ * ’)}
term term / f {print (‘ / ’)}
term f
f (expr)
f digit
digit 0
digit 1
digit 9
1
1
Rules

7. 7
2.3.5 Translation Schemes
Rules

8. 8
2.4 Parsing

9. 9
2.4 Parsing