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Hello.
Readihg http://martin.jambon.free.fr/extend-ocaml-syntax.html, I
attempt to solve the exercise from chapter 13:
"Suggested exercise: implement and test a syntax extension which supports a
where construct. For instance,
a + b where a = 1 and b = 2
means
let a = 1 and b = 2 in a + b
We decide that
let a = 1 in a where a = 2
should be read as
let a = 1 in (a where a = 2) (* returns 2 *)
and not
(let a = 1 in a) where a = 2 (* returns 1 *)
Also, the where construct is right-associative:
x + y where x = y where y = 1
means
x + y where x = (y where y = 1) (* depends on an external y *)
and not
(x + y where x = y) where y = 1 (* returns 2 *)"
I wrote (for old camlp4/camlp5):
EXTEND
expr: LEVEL "expr1"
[ RIGHTA
[ x = SELF; "where"; lb = V (LIST1 let_binding SEP "and") ->
<:expr< let $_list:lb$ in $x$ >> ]
];
END
but it does not satisfy the second suggestion. How can I have true RIGHTA
associative?
Thanks!
ermine