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StructuredFormatting
f#parsing

I'm stuggling with this when if comes to handling lists. I've had a stab at adding formatting to some of the
sample fsyacc/fslex programs out there, but am stuck as how to format lists.

Using the ast.fs from the parsing sample in the distribution, I've got as far as :-

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// Copyright (c) Microsoft Corporation 2005-2006.
// This sample code is provided "as is" without warranty of any kind. 
// We disclaim all warranties, either express or implied, including the 
// warranties of merchantability and fitness for a particular purpose. 
open StructuredFormat
open StructuredFormat.LayoutOps
let get_layout (env: #IEnvironment) (e: #IFormattable) = e.GetLayout(env)
type expr = 
	| Val of string 
	| Int of int
	| Float of float
	| Decr of expr
	with 
		interface StructuredFormat.IFormattable with
			member x.GetLayout(env) =
				match x with
				| Val s -> objL (box s)
				| Int i -> objL (box i)
				| Float f -> objL (box f)
				| Decr f -> objL (box f)
	end
end

type stmt = 
	| Assign of string * expr
	| While of expr * stmt
	| Seq of stmt list
	| IfThen of expr * stmt
	| IfThenElse of expr * stmt * stmt
	| Print of expr
	with 
		interface StructuredFormat.IFormattable with
			member x.GetLayout(env) =
				match x with
				| Assign (t1, t2) ->
					wordL t1 ++ wordL "=" ++ get_layout env t2
				| While (t1, t2) ->
					wordL "while" ++ get_layout env t1 ++ get_layout env t2
				 
				//| Seq (t1 ) -> commaListL List.map( fun n -> get_layout env n  ) t1 
				| Seq (t1 ) -> Seq.fold ( fun acc item -> acc @@- get_layout env item ) emptyL t1 
				| IfThen( t1, t2) ->
					wordL "if" ++ get_layout env t1 ++ wordL "then" ++ get_layout env t2
				| IfThenElse( t1, t2, t3) ->
					wordL "if" ++ get_layout env t1 ++ wordL "then" ++ get_layout env t2 ++ wordL "else" ++ get_layout env t3 
				| Print( t1 ) ->
					wordL "print" ++ get_layout env t1 
		end
end
type prog = Prog of stmt list



but cannot get commaListL or any of the other list wrappers to work.
All help appreciated.

Mark

.

OK, sorted out the issue, more to do with the correct application of brackets to nested function calls rather than anything else.
If any-one wants the code here it is (NOTE DECR doesn't appear in the supplied code - it's something I added as an experiment ) :-

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// Copyright (c) Microsoft Corporation 2005-2006.
// This sample code is provided "as is" without warranty of any kind. 
// We disclaim all warranties, either express or implied, including the 
// warranties of merchantability and fitness for a particular purpose. 
open StructuredFormat
open StructuredFormat.LayoutOps

let get_layout (env: #IEnvironment) (e: #IFormattable) = e.GetLayout(env)

type expr = 
	| Val of string 
	| Int of int
	| Float of float
	| Decr of expr
	with 
		interface StructuredFormat.IFormattable with
			member x.GetLayout(env) =
				match x with
				| Val s -> objL (box s)
				| Int i -> objL (box i)
				| Float f -> objL (box f)
				| Decr t1 -> wordL "decr" $$ leftL "(" $$ get_layout env t1 $$ rightL ")"
		end
end

type stmt = 
	| Assign of string * expr
	| While of expr * stmt
	| Seq of stmt list
	| IfThen of expr * stmt
	| IfThenElse of expr * stmt * stmt
	| Print of expr
	with 
		interface StructuredFormat.IFormattable with
			member x.GetLayout(env) =
				match x with
					| Assign (t1, t2) ->
				wordL t1 ++ wordL "=" ++ get_layout env t2
					| While (t1, t2) ->
				wordL "while" ++ get_layout env t1 @@-- get_layout env t2
					| Seq (t1 ) -> wordL "begin" @@ aboveListL ( List.map ( fun n -> get_layout env n $$ wordL ";" ) t1 ) @@ wordL "end"
					| IfThen( t1, t2) ->
				wordL "if" ++ get_layout env t1 ++ wordL "then" @@-- get_layout env t2
					| IfThenElse( t1, t2, t3) ->
				wordL "if" ++ get_layout env t1 ++ wordL "then" @@-- get_layout env t2 ++ wordL "else" @@-- get_layout env t3 
					| Print( t1 ) ->
					wordL "print" ++ get_layout env t1 
		end
end

type prog = Prog of stmt list
	with 
		interface StructuredFormat.IFormattable with
			member x.GetLayout(env) =
				match x with
				| Prog (t1 ) -> aboveListL ( List.map ( fun n -> get_layout env n $$ wordL ";" ) t1 )
		end
end


Enjoy..................................
Mark

By on 3/20/2008 8:30 AM ()

Microsoft.FSharp.Text.StructuredFormat.LayoutOps.Layout is marked as deprecated:

warning FS0044: This construct is deprecated. This property will be removed from the F# library and should no longer be used. Object formatting can be implemented by using the default rules of the printfn '%A' format, overriding the 'ToString' method on a type, registering a printer in F# Interactive or by creating a .NET debugger visualizer for your type

What should be done, then, when printing out expression trees (like the example above)? Are there some alternative pretty printing utilities available, or in the pipeline?

By on 3/19/2009 10:34 AM ()

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