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Simple Language (SL)

Simple Language (SL). Start version 00. Content. SL, the language AG, attribute grammar system First version of SL compiler written in AG. SL examples. let fac :: Int -&gt; Int = <br> -&gt; if n &gt; 0 then n * fac (n-1) else 1

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Simple Language (SL)

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  1. Simple Language (SL) Start version 00

  2. Content • SL, the language • AG, attribute grammar system • First version of SL compiler written in AG IPT - SL

  3. SL examples let fac :: Int -> Int = \n -> if n > 0 then n * fac (n-1) else 1 fi in fac 6 ni let fac :: Int -> Int = \n -> let cnt :: Ref Int = new 2 ; res :: Ref Int = new 1 in while ( cnt <= n ) do res := res * cnt ; cnt := cnt + 1 od ; res ni in fac 6 ni IPT - SL

  4. SL features • Expression evaluation • Int, Bool, Array, Product, Data, Ref • Assignment • Let (blocks), Lambda (functions) • If, While, Case • Typechecking IPT - SL

  5. SL first version • Integer constant • Generating: listing + code 55 .sl 55 stdout LDC 55 TRAP 0 HALT .ssm IPT - SL

  6. AG: SL parser • Parser combinators + scanner pRoot = sem_Root_Root <$> pExpr pExpr = (sem_Expr_Intexpr . string2int) <$> pInteger string2int = foldl (\val dig -> (10*val + ord dig -ord '0')) 0 • Semantic functions? IPT - SL

  7. AG: SL abstract syntax • Abstract tree representation DATA Root | Root Expr DATA Expr | Intexpr Int Root Root Expr Intexpr 55 tree node tree node type tree node variant IPT - SL

  8. AG: SL aspects (attributes) • Pretty printed output & stack code Root Root pp synthesized attribute copied Expr Intexpr 55 pp text.show $ int • Described by ATTR Root [ || ppexpr: PP_Doc ] SEM Root | Root LHS . ppexpr = "expr_pp" SEM Expr [ || pp: PP_Doc ] | Intexpr LHS . pp = "text.show $ int" IPT - SL

  9. AG notation inherited  inh+synth  synthesized  Attribute type (Hugs or Node) ATTR Root [ | | ppexpr: PP_Doc ] SEM Root | Root LHS . ppexpr = "expr_pp" SEM Expr [ | | pp: PP_Doc ] | Intexpr LHS . pp = "text.show $ int" Attribute name Attribution (Hugs) text for definition, specific for:Node type, Node variant, Attribute, Direction IPT - SL

  10. AG compilation • Generates Haskell • Generate SL.hs from SL.ag compile "SL" allc • Datastructures, semantics, ... data Expr = Expr_Intexpr Int deriving Show -- semantic domains type T_Expr = (SCode,PP_Doc) -- catas sem_Expr (Expr_Intexpr int) = sem_Expr_Intexpr int -- funcs sem_Expr_Intexpr ::Int -> T_Expr sem_Expr_Intexpr int = ( ((S_LDC int:)), (text.show $ int) ) IPT - SL

  11. Scanner • Transforms character sequences to tokens data TokenType = TkSymbol | TkVarid | TkConid | TkKeyword | TkOp | TkString | TkCharb| TkInteger8 | TkInteger10 | TkInteger16 | TkTextnm | TkTextln | TkError deriving (Eq, Ord) type Linenumber = Int type Filename = String newtype Token = Tok (TokenType, String, String, Linenumber, Filename) IPT - SL

  12. Code Generation • For a Simple Stack Machine SEM Root [ || ppscode: PP_Doc ] | Root LHS . ppscode = "( vlist . map (text.textOfS)" ". expr_scode" ". (S_TRAP 0:)" ". (S_HALT:)" "$ []" ")" SEM Expr [ || scode: SCode ] | Intexpr LHS . scode = "(S_LDC int:)" DATA S | HALT | TRAP Int | LDC Int IPT - SL

  13. Simple Stack Machine • Memory (Code, Stack) + Registers + Stack manipulating instructions IPT - SL

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