Question

How to apply log function top a list of emelent in array?

Answer 1

Array Functions
Arrays are also a big part of the Perl language and Perl has a lot of functions to help you work with them. Some of the actions arrays perform include deleting elements, checking for the existence of an element, reversing all of the the elements in an array, and sorting the elements.

Here are the functions you can use with arrays:

defined(VARIABLE) -- Returns true if VARIABLE has a real value and if the variable has not yet been assigned a value. This is not limited to arrays; any data type can be checked. Also see the exists function for information about associative array keys.
delete(KEY) -- Removes the key-value pair from the given associative array. If you delete a value from the %ENV array, the environment of the current process is changed, not that of the parent.
each(ASSOC_ARRAY) -- Returns a two-element list that contains a key and value pair from the given associative array. The function is mainly used so you can iterate over the associate array elements. A null list is returned when the last element has been read.
exists(KEY) -- Returns true if the KEY is part of the specified associative array. For instance, exists($array{"Orange"}) returns true if the %array associative array has a key with the value of "Orange."
join(STRING, ARRAY) -- Returns a string that consists of all of the elements of ARRAY joined together by STRING. For instance, join(">>", ("AA", "BB", "cc")) returns "AA>>BB>>cc".
keys(ASSOC_ARRAY) -- Returns a list that holds all of the keys in a given associative array. The list is not in any particular order.
map(EXPRESSION, ARRAY) -- Evaluates EXPRESSION for every element of ARRAY. The special variable $ is assigned each element of ARRAY immediately before EXPRESSION is evaluated.
pack(STRING, ARRAY) -- Creates a binary structure, using STRING as a guide, of the elements of ARRAY. You can look in the next Chapter on References for more information.
pop(ARRAY) -- Returns the last value of an array. It also reduces the size of the array by one.
push(ARRAY1, ARRAY2) -- Appends the contents of ARRAY2 to ARRAY1. This increases the size of ARRAY1 as needed.
reverse(ARRAY) -- Reverses the elements of a given array when used in an array context. When used in a scalar context, the array is converted to a string, and the string is reversed.
scalar(ARRAY) -- Evaluates the array in a scalar context and returns the number of elements in the array.
shift(ARRAY) -- Returns the first value of an array. It also reduces the size of the array by one.
sort(ARRAY) -- Returns a list containing the elements of ARRAY in sorted order. See next Chapter 8on References for more information.
splice(ARRAY1, OFFSET, -- Replaces elements of ARRAY1 with elements LENGTH, ARRAY2)in ARRAY2. It returns a list holding any elements that were removed. Remember that the $[ variable may change the base array subscript when determining the OFFSET value.
split(PATTERN, STRING, LIMIT) -- Breaks up a string based on some delimiter. In an array context, it returns a list of the things that were found. In a scalar context, it returns the number of things found.
undef(VARIABLE) -- Always returns the undefined value. In addition, it undefines VARIABLE, which must be a scalar, an entire array, or a subroutine name.
unpack(STRING, ARRAY) -- Does the opposite of pack().
unshift(ARRAY1, ARRAY2) -- Adds the elements of ARRAY2 to the front of ARRAY1. Note that the added elements retain their original order. The size of the new ARRAY1 is returned.
values(ASSOC_ARRAY) -- Returns a list that holds all of the values in a given associative array. The list is not in any particular order.
As with the string functions, only a few of these functions will be explored.

Example: Printing an Associative Array

The each() function returns key, value pairs of an associative array one-by-one in a list. This is called iterating over the elements of the array. Iteration is a synonym for looping. So, you also could say that the each() function starts at the beginning of an array and loops through each element until the end of the array is reached. This ability lets you work with key, value pairs in

};



sub createPair{

my($key, $value) = @_ ;



while (defined($array{$key})) {

$key++;

}



$array{$key} = $value;

};
This program prints:

100, Miles Davis

101, John Coltrane

200, Keith Jarrett
You can see that the number for John Coltrane has been changed to 101