Re: [Caml-list] scanf question

[Benoit Vaugon <benoit.vaugon@gmail.com>]

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Oups, I confirm it is a bug appearing when we have separated 
formatting_gen to formatting_lit in the implementation of formats to 
handle Format constructions like "@{<%s>" and "@[<hov %d>" that collides 
with scanf constructions like "%s@{" and "%s@[". I attach a patch (+ 6 
lines) that fix the problem, if somebody have time to integrate it...

Sorry.
Benoît.



Le 21/02/2015 10:55, Gabriel Scherer a écrit :
> This seems to be a regression caused by the reimplementation of format 
> strings in 4.02; some "stop after this character" indications are 
> supported, but some other fail (when they correspond to valid Format 
> specifications). Would you mind opening a but report ( 
> http://caml.inria.fr/mantis/ )?
>
> On Fri, Feb 20, 2015 at 8:28 PM, Milan Stanojević <milanst@gmail.com 
> <mailto:milanst@gmail.com>> wrote:
>
>     I want to parse a bash like sequence string, for example
>     "some-thing{1..20}", and extract the string before first { and then
>     two numbers inside.
>
>     I tried this first
>     utop # Scanf.sscanf "some-thing{1..3}" "%s{%d..%d}" (fun s n1 n2
>     -> s,n1,n2);;
>     Exception: End_of_file.
>
>     Then I realized %s is special and needs scanning indication
>     (character @).
>
>     So I tried that but I get the same error
>     utop # Scanf.sscanf "some-thing{1..3}" "%s@{%d..%d}" (fun s n1 n2
>     -> s,n1,n2);;
>     Exception: End_of_file.
>
>     But if I use some other character as end of string indication then
>     it works.
>     utop # Scanf.sscanf "some-thingI{1..3}" "%s@I{%d..%d}" (fun s n1 n2 ->
>     s,n1,n2);;
>     - : bytes * int * int = ("some-thing", 1, 3)
>
>     It seems '{' is somehow special but I can't find anything in the docs
>     about this.
>     Can someone explain what is going on here?
>
>     Thanks!
>
>
>     p.s. At the end I solved my thing by using a range
>
>     utop # Scanf.sscanf "some-thing{1..3}" "%[a-z-]{%d..%d}" (fun s n1 n2
>     -> s,n1,n2);;
>     - : bytes * int * int = ("some-thing", 1, 3)
>
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>


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diff -Naur old/stdlib/scanf.ml new/stdlib/scanf.ml
--- old/stdlib/scanf.ml	2015-02-21 20:38:02.250636479 +0100
+++ new/stdlib/scanf.ml	2015-02-21 20:53:51.486677851 +0100
@@ -1125,6 +1125,12 @@
     let scan width _ ib = scan_string (Some stp) width ib in
     let str_rest = String_literal (str, rest) in
     pad_prec_scanf ib str_rest readers pad No_precision scan token_string
+  | String (pad, Formatting_gen (Open_tag (Format (fmt', _)), rest)) ->
+    let scan width _ ib = scan_string (Some '{') width ib in
+    pad_prec_scanf ib (concat_fmt fmt' rest) readers pad No_precision scan token_string
+  | String (pad, Formatting_gen (Open_box (Format (fmt', _)), rest)) ->
+    let scan width _ ib = scan_string (Some '[') width ib in
+    pad_prec_scanf ib (concat_fmt fmt' rest) readers pad No_precision scan token_string
   | String (pad, rest) ->
     let scan width _ ib = scan_string None width ib in
     pad_prec_scanf ib rest readers pad No_precision scan token_string