![Example of simple code transformation
foo
| result a b |
a := 2.
b := 3.
result := a >= b
ifTrue: [ a ]
ifFalse: [ b ]
foo
| result a b |
a := 2.
b := 3.
result := a max: b
Source code Resulting code
2
transformation](https://image.slidesharecdn.com/2-151027170510-lva1-app6891/85/Code-Transformation-by-Direct-Transformation-of-ASTs-2-320.jpg)
![Find & Replace
“…code…”
x >= y
ifTrue: [ x ]
ifFalse: [ y ]
“…code…”
“…code…”
x max: y
“…code…”
4
Right-Hand Side partLeft-Hand Side part](https://image.slidesharecdn.com/2-151027170510-lva1-app6891/85/Code-Transformation-by-Direct-Transformation-of-ASTs-4-320.jpg)
![“Scary” transformation rule
Left-Hand Side part
| `@temporaries |
`.InitializationStatement.
`@condition1
ifTrue: [
| `@otherTemporaries |
`@.Statements.
`@condition2
ifTrue: [ ``@value := ``@calculate ]
ifFalse: [ ``@value := `#wrongLiteral ] ]
Right-Hand Side part
| `@temporaries `@otherTemporaries |
`.InitializationStatement.
`@condition1
ifFalse: [ ^self ].
`@.Statements.
``@value := `@condition2
ifTrue: [ ``@calculate ]
ifFalse: [ `#wrongLiteral ]
8](https://image.slidesharecdn.com/2-151027170510-lva1-app6891/85/Code-Transformation-by-Direct-Transformation-of-ASTs-8-320.jpg)
Code Transformation by Direct Transformation of ASTs
- 1. Code Transformation by Direct Transformation of ASTs M. Rizun, J.-C. Bach, S. Ducasse 1
- 2. Example of simple code transformation foo | result a b | a := 2. b := 3. result := a >= b ifTrue: [ a ] ifFalse: [ b ] foo | result a b | a := 2. b := 3. result := a max: b Source code Resulting code 2 transformation
- 3. Manual code transformation process (in big system) Replace all found occurrences by target code. Search for all occurrences of the code to replace in the source code. Definition of the desired target code. (RHS) Definition of the code to change. (LHS) 3
- 4. Find & Replace “…code…” x >= y ifTrue: [ x ] ifFalse: [ y ] “…code…” “…code…” x max: y “…code…” 4 Right-Hand Side partLeft-Hand Side part
- 5. Problems Time-consuming and annoying task. Complex and error-prone process. Rules are not reusable. 5
- 6. Tools to automate process Tool Create transformation rules. Apply rules on desired environment scope. Save rules for later reuse. 6
- 7. Rewrite Engine Engine for code transformation Unintuitive syntax & no GUI to apply rules Pros Cons 7
- 8. “Scary” transformation rule Left-Hand Side part | `@temporaries | `.InitializationStatement. `@condition1 ifTrue: [ | `@otherTemporaries | `@.Statements. `@condition2 ifTrue: [ ``@value := ``@calculate ] ifFalse: [ ``@value := `#wrongLiteral ] ] Right-Hand Side part | `@temporaries `@otherTemporaries | `.InitializationStatement. `@condition1 ifFalse: [ ^self ]. `@.Statements. ``@value := `@condition2 ifTrue: [ ``@calculate ] ifFalse: [ `#wrongLiteral ] 8
- 9. Inattention causes impactful mistakes! `.InitializationStatement `InitializationStatement 9
- 10. 10 How to apply rules?
- 11. OR | rule result aCollection anEnvironment | aCollection := self environment. anEnvironment := RBClassEnvironment classes: aCollection. rule := (Smalltalk globals at: self rules selectedItem) new. result := RBSmalllintChecker runRule: rule onEnvironment: anEnvironment. (ChangesBrowser changes: result builder changes) open 11
- 12. Rewrite Tool ´ Intuitive GUI ´ Real time result ´ Apply rules to any scope you want ´ Save rules for later reuse 12
- 13. A. Input code B. Resulting code C. LHS part of rule D. RHS part of rule 13
- 15. 15 Live Demo
- 16. 16 Download & Info ´ http://smalltalkhub.com/#!/~MarkRizun/RewriteTool ´ Configuration Browser (Pharo4) ´ http://myfuncoding.com ´ Pharo For The Enterprise (RewriteTool chapter) https://github.com/SquareBracketAssociates/PharoForTheEnterprise-english/tree/master/RewriteTool
- 17. Mark Rizun e-mail: mrizun@gmail.com blog: http://myfuncoding.blogspot.com/ 17