![Parser.
Tokens
Identifier
^[A-Za-z][A-Za-z_0-9]{0,255}$
Integer Const
^[+-]?d{1,10}$
Float Const
^([+-]?((d+.d+)|(d+.d+e[+-]d+)))$
String Literal
^'.{0,65535}'$](https://image.slidesharecdn.com/languageprocessorusingpython-131112035813-phpapp01/85/Language-processor-implementation-using-python-6-320.jpg)
![Algorythm of Analyzing
Lexems
def getClass(self, word):
c = None
if ((word in self.KeyWords)
or (word in metadata["delimiters"])
or (word in metadata["double"])
or (word in metadata["conditional_delimiters"])
or (word in metadata["multiplicative"])
or (word in metadata["additive"])
or (word in metadata["Relation"])):
c = word
else:
for r in self.RegExp.keys():
if re.compile(r).match(word):
c = self.RegExp[r]
return c](https://image.slidesharecdn.com/languageprocessorusingpython-131112035813-phpapp01/85/Language-processor-implementation-using-python-7-320.jpg)
![Configuration Format of Language
Grammar
EBNF
rule
program ::=
EBNF
Program ID ; block .
rule in configuration
programme:
- [program, id, ;, Block, "."]](https://image.slidesharecdn.com/languageprocessorusingpython-131112035813-phpapp01/85/Language-processor-implementation-using-python-12-320.jpg)
![Semantic Analyzer. Semantic
Actions
Rule
without semantic actions
complex_action:
- [begin, action_list, end]
Rule
with semantic actions
complex_action:
- [begin, "#200", action_list, end, "#220"]](https://image.slidesharecdn.com/languageprocessorusingpython-131112035813-phpapp01/85/Language-processor-implementation-using-python-13-320.jpg)
![Intermediary code
generation
We
are using tetrads language in order to generate
intermediary code
How tetrads language looks:
Z := X op Y
Z := op X
Z := Y
Z := Y[X]
Z:
GOTO Z
If condition GOTO Z](https://image.slidesharecdn.com/languageprocessorusingpython-131112035813-phpapp01/85/Language-processor-implementation-using-python-16-320.jpg)
Language processor implementation using python
- 1. Language Processor Implementation using Python
- 2. Objectiv e Implement parser, syntax analyzer, semantic analyzer for Pascal language Show main approaches to implementation of semantic analysis as well as intermediary code generation Parameterize language processor
- 3. Choosing Programming Language I investigated strong and week points of several programming languages: Java Perl Python C++ Delphi As a result I chose Python due to several very good reasons.
- 4. Python Benefits High level programming language Supports object oriented paradigm Convenient data types Relatively fast due to using C based libraries Easy readable syntax Cross-platform Convenient tools for parsing YAML Supports regular expressions out of the box
- 5. Language Processor Work Scheme Entry Parser Syntax Semantics Code gen Exit Вихід In memory tables
- 6. Parser. Tokens Identifier ^[A-Za-z][A-Za-z_0-9]{0,255}$ Integer Const ^[+-]?d{1,10}$ Float Const ^([+-]?((d+.d+)|(d+.d+e[+-]d+)))$ String Literal ^'.{0,65535}'$
- 7. Algorythm of Analyzing Lexems def getClass(self, word): c = None if ((word in self.KeyWords) or (word in metadata["delimiters"]) or (word in metadata["double"]) or (word in metadata["conditional_delimiters"]) or (word in metadata["multiplicative"]) or (word in metadata["additive"]) or (word in metadata["Relation"])): c = word else: for r in self.RegExp.keys(): if re.compile(r).match(word): c = self.RegExp[r] return c
- 8. Attribute Table Separate class Design pattern Singleton Uses hash table as internal structure Fast access Convenient format
- 10. Syntax Analyzer Context free grammar Left associated grammar EBNF Configuration format is yaml Language grammar is easily changed without source code modification
- 11. YAML Configuration Format Benefits Short and readable yaml uses data structures that are native to programming languages like Perl, Python
- 12. Configuration Format of Language Grammar EBNF rule program ::= EBNF Program ID ; block . rule in configuration programme: - [program, id, ;, Block, "."]
- 13. Semantic Analyzer. Semantic Actions Rule without semantic actions complex_action: - [begin, action_list, end] Rule with semantic actions complex_action: - [begin, "#200", action_list, end, "#220"]
- 14. Attribute classes Making code generation process easier, I created a bunch of classes like AttrFor. class AttrFor (AttrObject): self.parameter = None self.first = None self.last = None self.step = None self.body = None
- 16. Intermediary code generation We are using tetrads language in order to generate intermediary code How tetrads language looks: Z := X op Y Z := op X Z := Y Z := Y[X] Z: GOTO Z If condition GOTO Z
- 17. Example of input file program q; var a, b: integer; i: integer; d: integer; begin d := 4; for i:= 1 to (2+2*2)*2 do begin b:=b + 1; a:=a * 2; end; d:=a; end.
- 18. Output of language processor using intermediary code d:=4 i:=1 @Lid1: if i > 12 goto @Lid2 b:=b + 1 a:=a * 2 i := i + 1 goto @Lid1 @Lid2: d:=a
- 19. Bottom line I implemented parser, syntax analyzer, semantic analyzer, intermediary code generation of Pascal programming language I showed main concepts of semantic analysis as well as intermediary code generation Language processor has been parameterized