Quotations to A-Normal form

Quotations to A-Normal form based on http://matt.might.net/articles/a-normalization/

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// Quotations to A-Normal form
// based on http://matt.might.net/articles/a-normalization/

open System
open Microsoft.FSharp.Quotations
open Microsoft.FSharp.Quotations.Patterns
 

let rec normalize (expr : Expr) (k : Expr -> Expr) : Expr = 
    match expr with
    | Var var -> k expr
    | Value(value, _) -> k expr
    | Let (var, expr, body) -> 
        normalize expr (fun expr' -> Expr.Let(var, expr', normalize body k))
    | Lambda (var, body) -> 
        k <| Expr.Lambda (var, normalize body id)
    | Application (exprF, arg) -> 
        normalizeName exprF (fun exprF' -> normalizeName arg (fun arg' -> k <| Expr.Application(exprF', arg')))  
    | IfThenElse (pred, trueExpr, falseExpr) -> 
        normalizeName pred (fun pred' -> 
        k <| Expr.IfThenElse (pred', normalize trueExpr id, normalize falseExpr id))
    | _ -> failwithf "Not supported, expr: %A" expr

and normalizeName (expr : Expr) (k : Expr -> Expr) : Expr = 
    normalize expr (fun expr' -> 
        match expr' with
        | Var var -> k expr'
        | Value(value, _) -> k expr'
        | _ -> let var = new Var("temp", expr'.Type)
               Expr.Let(var, expr', k <| Expr.Var var))

// Examples
normalize <@ let x = let y = 1 in y in x @> id
normalize <@ if (let x = true in x) then 1 else 2 @> id
normalize <@ (fun f x -> f x) ((fun x -> x) (fun x -> x)) 1 @> id

namespace System

namespace Microsoft

namespace Microsoft.FSharp

namespace Microsoft.FSharp.Quotations

module Patterns

from Microsoft.FSharp.Quotations

val normalize : expr:Expr -> k:(Expr -> Expr) -> Expr

Full name: Script.normalize

val expr : Expr

Multiple items
type Expr =
  override Equals : obj:obj -> bool
  member GetFreeVars : unit -> seq<Var>
  member Substitute : substitution:(Var -> Expr option) -> Expr
  member ToString : full:bool -> string
  member CustomAttributes : Expr list
  member Type : Type
  static member AddressOf : target:Expr -> Expr
  static member AddressSet : target:Expr * value:Expr -> Expr
  static member Application : functionExpr:Expr * argument:Expr -> Expr
  static member Applications : functionExpr:Expr * arguments:Expr list list -> Expr
  ...

Full name: Microsoft.FSharp.Quotations.Expr

--------------------
type Expr<'T> =
  inherit Expr
  member Raw : Expr

Full name: Microsoft.FSharp.Quotations.Expr<_>

val k : (Expr -> Expr)

Multiple items
active recognizer Var: Expr -> Var option

Full name: Microsoft.FSharp.Quotations.Patterns.( |Var|_| )

--------------------
type Var =
  interface IComparable
  new : name:string * typ:Type * ?isMutable:bool -> Var
  member IsMutable : bool
  member Name : string
  member Type : Type
  static member Global : name:string * typ:Type -> Var

Full name: Microsoft.FSharp.Quotations.Var

--------------------
new : name:string * typ:Type * ?isMutable:bool -> Var

val var : Var

active recognizer Value: Expr -> (obj * Type) option

Full name: Microsoft.FSharp.Quotations.Patterns.( |Value|_| )

val value : obj

active recognizer Let: Expr -> (Var * Expr * Expr) option

Full name: Microsoft.FSharp.Quotations.Patterns.( |Let|_| )

val body : Expr

val expr' : Expr

static member Expr.Let : letVariable:Var * letExpr:Expr * body:Expr -> Expr

active recognizer Lambda: Expr -> (Var * Expr) option

Full name: Microsoft.FSharp.Quotations.Patterns.( |Lambda|_| )

static member Expr.Lambda : parameter:Var * body:Expr -> Expr

val id : x:'T -> 'T

Full name: Microsoft.FSharp.Core.Operators.id

active recognizer Application: Expr -> (Expr * Expr) option

Full name: Microsoft.FSharp.Quotations.Patterns.( |Application|_| )

val exprF : Expr

val arg : Expr

val normalizeName : expr:Expr -> k:(Expr -> Expr) -> Expr

Full name: Script.normalizeName

val exprF' : Expr

val arg' : Expr

static member Expr.Application : functionExpr:Expr * argument:Expr -> Expr

active recognizer IfThenElse: Expr -> (Expr * Expr * Expr) option

Full name: Microsoft.FSharp.Quotations.Patterns.( |IfThenElse|_| )

val pred : Expr

val trueExpr : Expr

val falseExpr : Expr

val pred' : Expr

static member Expr.IfThenElse : guard:Expr * thenExpr:Expr * elseExpr:Expr -> Expr

val failwithf : format:Printf.StringFormat<'T,'Result> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.failwithf

property Expr.Type: Type

static member Expr.Var : variable:Var -> Expr

val x : int

val y : int

val x : bool

val f : (int -> int)

val x : (int -> int)

Raw view Test code New version

More information

Link:	http://fssnip.net/7QW
Posted:	7 years ago
Author:	Nick Palladinos
Tags:	#quotations