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[Andrei Arusoaie <andrei.arusoaie AT gmail.com>]

Hi Seyed,

Because we rely on Maude parsing, which is not necessarily the best choice, sometimes we get into this kind of errors... 

What you can do is to add precedences to you syntactical constructs. 

For instance, this is how it worked for me:

mac:exp andreiarusoaie$ cat exp-lambda.k

require exp

require /modules/substitution

module EXP-LAMBDA-SYNTAX

 imports EXP-SYNTAX

 

  syntax Val ::= #Int

                | "lambda" #Id "." Exp [binder prec 50]

 

  syntax Exp ::= Val

               | Exp Exp [seqstrict prec 60]

      | "mu" #Id "." Exp [binder]

 

  syntax Exp ::= "let" #Id "=" Exp "in" Exp

              | "letrec" #Id #Id "=" Exp "in" Exp

     

  macro (let X:#Id = E1:Exp in E2:Exp) = (lambda X.E2) E1

 

 end module

 

module EXP-LAMBDA

end module

mac:exp andreiarusoaie$ kompile exp-lambda.k 

Compiled version written in exp-lambda-compiled.maude.

mac:exp andreiarusoaie$

Notice that I've added the `prec` attribute to 'ambiguous' constructs: `"lambda" #Id "." Exp` and `Exp Exp` . `prec 50` says that `"lambda" #Id "." Exp` construct should be applied first, before any construct which has prec Y, where Y > 50. This is the reason I've added `prec 60` to `Exp Exp`.

Maybe our Maude expert, Traian, will come with a nicer solution. :-)

Andrei

2012/2/20 Seyed H. HAERI (Hossein) <hossein.haeri AT gmail.com>

Hi again,

Now, I have a new error message

<Err>
Error: "exp-lambda.maude", line 317 (mod EXP-LAMBDA-SYNTAX): didn't expect
to...

eq ( let X:#Id = E1:Exp in E2:Exp ) = ( lambda X . E2 ) <---*HERE*
Error: "exp-lambda.maude", line 316 (mod EXP-LAMBDA-SYNTAX): no parse for
st...

eq (let X:#Id = E1:Exp in E2:Exp) = (lambda X . E2) E1 [metadata
"location=(...
</Err>

for this bit of Fig 3:

<Code>
require exp
require /modules/substitution

module EXP-LAMBDA-SYNTAX
 imports EXP-SYNTAX

 syntax Val ::= #Int
              | "lambda" #Id "." Exp [binder]
 syntax Exp ::= Val
              | Exp Exp [seqstrict]
              | "mu" #Id "." Exp [binder]
 syntax Exp ::= "let" #Id "=" Exp "in" Exp
              | "letrec" #Id #Id "=" Exp "in" Exp

 macro (let X:#Id = E1:Exp in E2:Exp) =
   (lambda X.E2) E1
end module

module EXP-LAMBDA
end module
</Code>

I can't quite get it why Maude is unhappy with the parenthesisation. Any idea?

TIA,
--Hossein

--------------------------------------------------------------------------------------------------------------

Seyed H. HAERI (Hossein)

Research Assistant
Institute for Software Systems (STS)
Technical University of Hamburg (TUHH)
Hamburg, Germany

ACCU - Professionalism in programming - http://www.accu.org/
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--
Numai bine,

Andrei