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Date: Thu, 26 Mar 2009 17:53:08 +0100
From: Tiphaine Turpin <Tiphaine.Turpin@irisa.fr>
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Subject: printf "%a" vs sprintf "%a"
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X-Spam: no; 0.00; irisa:01 printf:01 sprintf:01 printf:01 sprintf:01 typing:01 functions:01 breaks:02 string:02 string:02 unit:03 unit:03 confused:04 simpler:05 channel:06 

Hi,

I'am confused by the interpretation of "%a":

# Printf.printf "%a";;
- : (out_channel -> '_a -> unit) -> '_a -> unit = <fun>
# Printf.sprintf "%a";;
- : (unit -> '_a -> string) -> '_a -> string = <fun>

Usually, the typing of formatting functions is such that

printf something

has type unit if and only if

sprintf something

has type string. But %a breaks this rule. Wouldn't it be simpler to have
two separate directives which accept respectively string printers and
channel printers, regardless of the outer printing function ?

Tiphaine