Perl | Automatic String to Number Conversion or Casting

Perl has a different way to deal with the operators because here operator defines how the operands will behave but in other programming languages, operands define how an operator behaves. Casting refers to the conversion of a particular variable’s data type to another data type. For example, if there is a string “1234” and after converting it to int data type the output will be an integer 1234. Conversion of string to integer in Perl has many ways. One is to use Typecasting, while the other one involves use of ‘sprintf‘ function. Sometimes people do not use the word casting in Perl because the whole thing of conversion is automatic.

Typecasting

Type conversion happens when we assign the value of one data type to another. If the data types are compatible, then Perl does Automatic Type Conversion. If not compatible, then they need to be converted explicitly which is known as Explicit Type conversion. There are two types of typecasting:

• Implicit Typecasting: Implicit type conversion is done by the compiler itself. There is no need for the user to mention a specific type conversion using any method. The compiler on its own determines the data type of the variable if required and fixes it. In Perl when we declare a new variable and assign a value to it, it automatically converts it into a required data type.

  Example 1:

  # Perl code to demonstrate implicit
  # type casting
  
  # variable x is of int type
  $x = 57;
  
  # variable y is of int type
  $y = 13;
  
  # z is an integer data type which
  # will contain the sum of x and y
  # implicit or automatic conversion
  $z = $x + $y;
  
  print "z is ${z}\n";
  
  # type conversion of x and y integer to
  # string due to concatenate function
  $w = $x.$y;
  
  # w is a string which has the value:
  # concatenation of string x and string y
  print "w is ${w}\n";

  Output:

  z is 70
  w is 5713
  

• Explicit Typecasting: In this conversion the user can cast a variable to a particular data type according to requirement. Explicit type conversion is required if the programmer wants a particular variable to be of a particular data type. It is important for keeping the code consistent so that no variable causes an error due to type conversion.

  Example: The following perform explicit typecasting where a string(or any data type) is converted to specified type(say int).

  # Perl code to demonstrate Explicit
  # type casting
  
  # String type
  $string1 = "27";
  
  # conversion of string to int
  # using typecasting int()
  $num1 = int($string1);
  
  $string2 = "13";
  
  # conversion of string to int
  # using typecasting int()
  $num2 = int($string2);
  
  print "Numbers are $num1 and $num2\n";
  
  # applying arithmetic operators
  # on int variables
  $sum = $num1 + $num2;
  
  print"Sum of the numbers = $sum\n";

  Output:

  Numbers are 27 and 13
  Sum of the numbers = 40
  

sprintf function

This sprintf function returns a scalar value, a formatted text string, which gets typecasted according to the code. The command sprintf is a formatter and doesn’t print anything at all.

# Perl code to demonstrate the use
# of sprintf function

# string type
$string1 = "25";

# using sprintf to convert
# the string to integer
$num1 = sprintf("%d", $string1);

$string2 = "13";

# using sprintf to convert
# the string to integer
$num2 = sprintf("%d", $string2);

# applying arithmetic operators
# on int variables
print "Numbers are $num1 and $num2\n";

$sum = $num1 + $num2;
print"Sum of the numbers = $sum\n";

Output:

Numbers are 25 and 13
Sum of the numbers = 38