CS212 Spring 2002
4/10/2002
Lecture 11: Abstract Syntax Trees ; Part 4 ; Software Engineering issues
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[0] Announcements:
+ Part 3 extended due date 4/15, 1:00:00 pm
+ have you noted Bali changes? things like declarations being INSIDE the {}
  (see online Announcements for full list)
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[1] Summary from last time:
+ compilers/translators
+ process of translation
+ parsing and expressions
+ abstract syntax trees
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[2] Overview
+ more on ASTs
+ OOP and ASTs for Part 4
+ software engineering issues
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[3] A bit more on Abstract Syntax Trees
+ 2 more examples from L10
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[4] Example ASTs for Sam-Code

+ int leaf



+ name leaf



+ expression




+ assignment statement




+ block (list)










+ 1-statement block







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[4] Example ASTs continued

+ selection statement






+ do-while repetition statement





+ return statement





+ more? 
  - generally, think node, list, and/or tree
  - will write along with Part 4
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[5] OOP Aspects
+ store Bali program as tree in the compiler
+ use ASTs for convenience and elegance

  // main idea:
  interface AST {
     String toString();
     String codeGen(Function F);
  }

  class BC {
  // read in functions
  // output sam-code
  }

  class Function implements AST {
  // stuff for you to write
  }

+ Grammar classes
  - write classes according to hierarchy
  - think of the grammar as tree
   
  abstract class Statement implements AST { }
  class Declaration extends Statement { }
  class Selection extends Statement { }
  // and more

+ how many trees are there? 2...don't confuse them:
  - AST for storing code
  - OOP design to write classes






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[6] Software Engineering Issues According to DIS

(A) Process of Programming

high-level: 
+ Problem -> Approach -> Solution
+ iterate if necessary

medium-level:
+ programming as writing
+ brainstorm, research, outline, draft, rewrite, polish
  - brainstorm
  - research: traditional research, class formation
  - outline: algorithms
  - draft
  - rewrite: iteration
  - polish: bells and whistles
  
low-level:
+ stepwise refinement: "baby steps"
+ stubbing
+ top-down
+ bottom-up

tricks of the trade
- how to stub
- commenting as you go/partial debugging
- mixing top-down/bottom up
- personal reuse database