On Feb 19, 2005, at 4:07 PM, Gert Cuykens wrote:
On Sat, 19 Feb 2005 02:57:53 -0700, Chad Leigh -- Shire. Net LLC <[EMAIL PROTECTED]> wrote:
On Feb 19, 2005, at 2:51 AM, Gert Cuykens wrote:
On Thu, 17 Feb 2005 13:17:51 +0100, Hubert Sokołowski <[EMAIL PROTECTED]> wrote:On Thu, 17 Feb 2005 13:05:43 +0100 Gert Cuykens <[EMAIL PROTECTED]> wrote:
static void callback( GtkWidget *widget, gpointer data ){ g_print ("Hello again - %s was pressed\n", (gchar *) data); }
why do they put () around gchar ? why can it not be gchar *data ?
You should learn some more about programming in C before you start writing GTK apps.
hs
Does anybody want to explain what the () thingies are around gchar * ?
It is a typecast -- coercing "data" to be of type (gchar *) to the compiler when matching parameter types at compiler time.
Chad
lol :) I wish you could see the expression on my face while reading it :)
Why can i not do this ?
g_print ("Hello again - %s was pressed\n", gchar *data); or this gchar *data; g_print ("Hello again - %s was pressed\n", *data); or this gchar *data; g_print ("Hello again - %s was pressed\n", data);
What does coercing mean ? Why does the compiler have to match parameters ?
I'll let you look up the answers above in C reference manuals (and C++ ones for by reference parameters). However, the answer to "Why" is best known to Kernighan and Ritchie <http://cm.bell-labs.com/cm/cs/cbook/>
C is (now) a strongly typed language and this type checking is done at compile time in order to try and help you reduce errors.
PS what is the difference between ?
Assuming the following declaration
gpointer data;
data is a pointer to some kind of structure
A=*data
this is the data itself, ie, the pointer is dereferenced
A=data
this is the pointer to the data
A=&data
this is a kind of double indirection -- this is a reference to the pointer to the data. I believe this sort of notation for a reference first came from Bjarne Stroustrop or however he spells it -- the "father" of C++
I am not a C nor C++ expert. I long ago stopped doing C++ and my C is mostly confined to Objective-C now-a-days. Best to get the latest K&R C book and a good C++ book to answer your questions.
best Chad
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