Lexical analysis program ( Lexical Analyzer ) requirements:
- stream from a source program composed of character scan left to right
- identify the lexical meaning of the word ( Lexemes )
- Return word record (word class, the word itself)
- filtered spaces
- skip comments
- lexical errors found
Program Structure:
Input: character stream (input what way, what data structure stored)
deal with:
- Traverse (What traversal)
- lexical rules
Output: word stream (what output form)
- tuple
Word class:
1. Identifier (10)
2. unsigned (11)
3. Leave the word (the word one yard)
4. Operator (word one yard)
5. delimiter (word one yard)
Word symbols |
Species do not code |
Word symbols |
Species do not code |
begin |
1 |
: |
17 |
if |
2 |
:= |
18 |
then |
3 |
< |
20 |
while |
4 |
<= |
21 |
do |
5 |
<> |
22 |
end |
6 |
> |
23 |
l(l|d)* |
10 |
>= |
24 |
dd* |
11 |
= |
25 |
+ |
13 |
; |
26 |
- |
14 |
( |
27 |
* |
15 |
) |
28 |
/ |
16 |
# |
0
|