Compiler Design

1. Compilers Design
Course
Ramadan Babers
Compilers Design – Lec4
Faculty of Science Helwan University
1st Term – 2017/2018

2. 2
Chapter 2
A Simple Syntax-Directed
Translator

3. 2.3 Syntax-Directed Translation
3
Syntax-directed translation is done by attaching rules or
program fragments to productions in a grammar.
two concepts related to syntax-directed translation:
 Attributes. An attribute is any quantity associated with a programming
construct.
 (Syntax-directed) translation schemes. A translation scheme is a notation
for attaching program fragments to the productions of a grammar.
We will use this concept

4. 2.3 Syntax-Directed Translation
4
Productions Semantic Rules
Grammar Rules
=

5. 5
Example: 1+2-3
2.3 Syntax-Directed Translation
Productions Semantic Rules
expr expr + term
expr expr - term
expr term
term 0
term 1
term 9
expr.t = expr.t + term.t
expr.t = expr.t – term.t
expr.t = term.t
term.t = 0
term.t = 1
term.t = 9

6. 6
Example: 1+2-3
2.3 Syntax-Directed Translation
Productions Semantic Rules
expr expr + term
expr expr - term
expr term
term 0
term 1
term 9
expr.t = expr .t + term.t
expr.t = expr .t – term.t
expr.t = term.t
term.t = 0
term.t = 1
term.t = 9
1
1
1
1

7. 2.3 Syntax-Directed Translation
7
expr
- termexpr
expr + term
term
1 2 3
Example: 1+2-3

8. 2.3 Syntax-Directed Translation
8
expr.t=0
- term.t=3expr.t=3
expr.t=1 + term.t=2
term.t=1
1 2 3
Example: 1+2-3
Annotated Parse Tree

9. 9
Example: 5-(2*1)+1
5 - ( 2 * 1 ) + 1
expr + term
expr - term
term factor
2.3 Syntax-Directed Translation

10. 10
Example: 5-(2*1)+1
2.3 Syntax-Directed Translation
Productions Semantic Rules
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 = 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

11. 11
Example: robot moves in 2 dimensions
ww =(-2,0)
2.3 Syntax-Directed Translation

12. 12
Example: robot moves in 2 dimensions
2.3 Syntax-Directed Translation
Productions Semantic Rules
block begin op.expr
op.expr E
op.expr expr
expr expr1 dir
expr dir
dir N
dir S
dir E
dir W
Block.x = begin.x + op.expr.x
Block.y = begin.y + op.expr.y
op.expr.x = 0
op.expr.y = 0
op.expr.x = expr.x
op.expr.y = expr.y
Expr.x = expr1.x + dir.x
Expr.y = expr1.y + dir.y
Expr.x = dir.x
Expr.y = dir.y
Dir.x = 0
Dir.y = 1