Perl calculate and average problem

[ed]

I'm trying to understand perl and I'm pretty much confused. I'm trying
to write a script that takes an array of numbers (arbitrary in size).
The function will calculate the average of the numbers, the total of
all the numbers added together, and a new array of numbers which is the
other numbers divided by 2. It will then return a new list with all of
the information, and a new array of number, the total. The script
file, should get a list of numbers from the user (either via STDIN or a
list of arguments.)

 

[Gunnar Hjalmarsson]

I'm trying to understand perl and I'm pretty much confused. I'm trying
to write a script that takes an array of numbers (arbitrary in size).
The function will calculate the average of the numbers, the total of
all the numbers added together, and a new array of numbers which is the
other numbers divided by 2. It will then return a new list with all of
the information, and a new array of number, the total. The script
file, should get a list of numbers from the user (either via STDIN or a
list of arguments.)

Thanks for letting us know.

Where is the code you've written?

Have you read the posting guidelines for this group?
http://mail.augustmail.com/~tadmc/clpmisc/clpmisc_guidelines.html

 

[ed]

Well here is what I have so far:

@params = (1,2,3,4,5,7,8,9);

foreach $digits(@params){
$total = numbers($digits);
print "$numbers\n";
}

sub numbers (){
my $digits = shift(@_);

foreach $params(@params){
$digits =+ @params;
}

return $total
}

I can't get the average of the array to even get to the other part of
the code to divide the total.

 

[Josef Moellers]

Well here is what I have so far:

# Tell us something more ...
use warnings;
use strict;

@params = (1,2,3,4,5,7,8,9);

foreach $digits(@params){
$total = numbers($digits);
print "$numbers\n";

Where does $numbers come from?
The above pragmas would have told you it isn't defined.

}

sub numbers (){
my $digits = shift(@_);

foreach $params(@params){
$digits =+ @params;

You _do_ know that @params in scalar context is the number of elements
in @params?

}

return $total
}

I can't get the average of the array to even get to the other part of
the code to divide the total.

Let's see if we can dig up something based upon your initial request:
"calculate the average of the numbers, the total of
all the numbers added together, and a new array of numbers which is the
other numbers divided by 2."

my $sum = 0, $avg = 0;
my @half;
foreach (@params) {
$sum += $_;
push @half, $_ / 2;
}
$avg = $sum / @params;
#
# $avg: the average of the numbers
# $sum: the total of all the numbers added together
# @half: a new array of numbers which is the other numbers divided by 2
print "average: ", $avg, "\n";
print "total: ", $sum, "\n";
print "new array: ", join(" ", @half), "\n";


I can't, for the heck of it, find out what you mean by
"It will then return a new list with all of
the information, and a new array of number, the total."

 

[Gunnar Hjalmarsson]

[ Please provide context when replying to a message, as the posting
guidelines recommend! Those who may be able to help don't usually access
this group via Google. ]

Well here is what I have so far:

Why didn't you make an attempt to follow the posting guidelines, when
your attention had been called to them?

Why did you choose to even ignore that question?

 

[ed]

The course I'm taking hasn't gotten to the use of warnings/strict but I
have read a little about it.
As far as the number go, my frustration level is way up there and I've
changed my script so many times that at this point not sure where
numbers came from.
The way I understand this "You _do_ know that @params in scalar context
is the number of elements in @params? " is that the the number is eight
(total elements), not the numbers 1,2,3,4,5,7,8,9? I was told to get a
list of numbers from STDIN or a list or arguments, is my array not the
correct way to go?

 

[A. Sinan Unur]

The course I'm taking hasn't gotten to the use of warnings/strict but
I have read a little about it.

Ask for your money back. The *first* step in writing any Perl program
must be to enable strictures and warnings.

Have you read the posting guidelines, yet. They explain how you can help
yourself, but more importanttly, help others help you.

As far as the number go, my frustration level is way up there and I've
changed my script so many times that at this point not sure where
numbers came from.

Well, you need to take five minutes, read the guidelines, and follow
them step by step. Then, go over your assignment, and come up with a
spec for your program which others can understand. Then, follow the spec
step by step to write it (with strictures and warnings enabled).

That way, when you his a snag, others will be able to help you.

The way I understand this "You _do_ know that @params in scalar
context is the number of elements in @params? " is that the the
number is eight (total elements), not the numbers 1,2,3,4,5,7,8,9?

If @params consists of (1, 2, 3, 4, 5, 6, 7, 8, 9), then @params has 9
elements. $params[0] is the first element. $params[8] is the last
element.

You'll need to start quoting an appropriate amount of context, and
responding to specific questions others have asked to have any hope of
staying out of killfiles.

Sinan

 

[axel]

Let's see if we can dig up something based upon your initial request:
"calculate the average of the numbers, the total of
all the numbers added together, and a new array of numbers which is the
other numbers divided by 2."

my $sum = 0, $avg = 0;

This should be either:

my $sum = 0, my $avg =0;
or

my ($sum, $avg);

otherwise $avg will fail 'use strict'.

Axel

 

[ed]

Thanks, I appreciate your help.

 

[Josef Moellers]

ed wrote:

Please (more visibly) quote some context when replying.

The course I'm taking hasn't gotten to the use of warnings/strict but I
have read a little about it.
As far as the number go, my frustration level is way up there and I've
changed my script so many times that at this point not sure where
numbers came from.
The way I understand this "You _do_ know that @params in scalar context
is the number of elements in @params? " is that the the number is eight
(total elements), not the numbers 1,2,3,4,5,7,8,9? I was told to get a
list of numbers from STDIN or a list or arguments, is my array not the
correct way to go?

Well, the choice of data structure surely is an important part of the
analysis and design phase of a program, but in Perl, an array would be a
good thing to use.

What I was aiming at was your use of @params here:

$digits =+ @params;

@params has a different meaning depending on whether it is used in list
context (where it denotes the entire array) or in scalar context (where
it denotes the number of elements in @params).
Finding out the current context is not always easy, but trying to add
something to a scalar definitely is scalar context and from your code,
adding the size of the array for each element of the array is definitely
not what you wanted to do.
It may also have been a mis-spelling, as

foreach $params(@params){

assigns each arramy element of "@params" to a scalar variable "$params",
so your code would have been better if you'd written

$digits += $params;

(I'd have use "$param" instead of "$params", as the variable contains a
single parameter only in each loop iteration).

Josef

 

[Tad McClellan]

Finding out the current context is not always easy,

Sure it is. You just replace the construct that you are wondering
about with:

context()

where

sub context {
warn wantarray() ? 'list context' : 'scalar context'
}

 

[John W. Krahn]

Sure it is. You just replace the construct that you are wondering
about with:

context()

where

sub context {
warn wantarray() ? 'list context' : 'scalar context'
}

You missed one Tad. ;-)

sub context {
warn defined wantarray() ? wantarray() ? 'list' : 'scalar' : 'void', '
context'
}



John