trapping file i/o error

[toylet]

In most perl examples, it used this method to trap error:

open(INFILE, $fname) or die "Unable to open $fname";
process_file();
close(INFILE)
other_codes();

Now that if I don't want to die after the open so as to run
other_codes()? Could I test the value of file handle INFILE like what I
did with C?

fhandle=fopen(f name,"r")
if (fhandle > 0) {
process_file();
fclose(fhandle)
}
else
show_error()
other_codes();

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/( _ )\ Linux 2.4.22-xfs
^ ^ 5:00pm up 2 days 18:54 load average: 1.00 1.00 1.00

[Ben Morrow]

toylet <toylet_at_mail .hongkong.com> wrote:

hmm... how do you force a variable into a certain context (could I also
call it "type casting")?
You almost never need to. About the time string/number matters is with
magic values like $!; other than that, scalar context can be forced with
scalar() or unary + and list context with parentheses ().
for integer, $i+0 or (int)$i.
yes no, though int($i) will give you int rather than
float
for string, $i+""? or is it (string)$i?
$i.'' or "$i" no
for array
for hash

eh what? Please explain what you expect, e.g., (hash)$i to achieve?

Ben

--
And if you wanna make sense / Whatcha looking at me for? (Fiona Apple)
* be*@morrow.me.u k *

[toylet]

>> for array

for hash

eh what? Please explain what you expect, e.g., (hash)$i to achieve?

Just asking for a general method of forcing context.

--
.~. Might, Courage, Vision. In Linux We Trust.
/ v \ http://www.linux-sxs.org
/( _ )\ Linux 2.4.22-xfs
^ ^ 3:24pm up 4:33 1 user 1.79 1.45

[Anno Siegel]

Ben Morrow <us****@morrow. me.uk> wrote in comp.lang.perl. misc:

toylet <toylet_at_mail .hongkong.com> wrote:

hmm... how do you force a variable into a certain context (could I also
call it "type casting")?
You almost never need to. About the time string/number matters is with
magic values like $!; other than that, scalar context can be forced with
scalar() or unary + and list context with parentheses ().

Parentheses only provide list context on the left side of an assignment
(anywhere else?). Watch this:

sub wanta { print wantarray ? "array\n" : "scalar\n" }

$x = wanta;
( $x) = wanta;
$x = ( wanta);
( $x) = ( wanta);

The parentheses on the right side don't seem to do anything.

I can't meaningfully say much about the difference between unary +
and scalar(), except that there is one. Vaguely, "+" can change parsing,
scalar() can't.

[...]
And if you wanna make sense / Whatcha looking at me for? (Fiona Apple)

Can't say I understand that sig of your's, but I like it :)

Anno

[Anno Siegel]

Ben Morrow <us****@morrow. me.uk> wrote in comp.lang.perl. misc:

toylet <toylet_at_mail .hongkong.com> wrote:

hmm... how do you force a variable into a certain context (could I also
call it "type casting")?
You almost never need to. About the time string/number matters is with
magic values like $!; other than that, scalar context can be forced with
scalar() or unary + and list context with parentheses ().

Parentheses only provide list context on the left side of an assignment
(anywhere else?). Watch this:

sub wanta { print wantarray ? "array\n" : "scalar\n" }

$x = wanta;
( $x) = wanta;
$x = ( wanta);
( $x) = ( wanta);

The parentheses on the right side don't seem to do anything.

I can't meaningfully say much about the difference between unary +
and scalar(), except that there is one. Vaguely, "+" can change parsing,
scalar() can't.

[...]
And if you wanna make sense / Whatcha looking at me for? (Fiona Apple)

Can't say I understand that sig of your's, but I like it :)

Anno

[Joe Smith]

toylet wrote:

for array
for hash

eh what? Please explain what you expect, e.g., (hash)$i to achieve?

Just asking for a general method of forcing context.

($a,$b) = foo(); # List context
@array = foo(); # List context
%hash = foo(); # List context
foo(); # Null context
$var = foo(); # Scalar context
$var = +foo(); # Numeric scalar context
$var = foo().""; # String scalar context
if (foo()) {}; # Boolean scalar context

-Joe

[Tassilo v. Parseval]

[ F'up set to clpm;
comp.lang.perl doesn't exist ]

Also sprach Joe Smith:

toylet wrote:

Just asking for a general method of forcing context.

($a,$b) = foo(); # List context
@array = foo(); # List context
%hash = foo(); # List context
foo(); # Null context
$var = foo(); # Scalar context
$var = +foo(); # Numeric scalar context

Nope. This does not force numeric context. This does:

$var = foo() + 0;

Or this:

$var = foo() * 1;

Any numeric operator in conjunction with the neutral element with
respect to the used operator can be used to enforce numeric context.

Tassilo
--
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