MultiPhaseExpr.md

Multi Phase Expression

Notes about refactoring expression compilation phases.

Old Phases

1. Undesugared ExprAST
2. Desugared BExpr
3. Resolved RExpr

New Phases

Later phases embed exprs in earlier phases: RExpr embeds BExpr embeds ExprAST. Module context (a lookup object) is attached to an expression itself.

data AnyLookup = forall a. Lookup a => AnyLookup a
data NExpr
  = NConst Value
  | NF AFName              -- ^ a function (absolute function name)
  | NApp AFlName [NExpr]   -- ^ a functional form (absolute functional name)
  | NRead Int              -- ^ get nth context variable
  | NPush NExpr            -- ^ push context variable
  | NBExpr AnyLookup BExpr

data BExpr
  = BConst Value
  | BF RFName              -- ^ a function (relative function name)
  | BApp RFlName [BExpr]   -- ^ a functional (relative functional name)
  | BWith AnyLookup BExpr  -- ^ with module
  | BExprAST ExprAST