Scalar Value Interpretation

Perl Tutorials - Herong's Tutorial Examples

∟Scalar Value Interpretation

This section describes how a scalar value will be interpreted in an operation. A tutorial example is provided to verify scalar value interpretation rules.

When a scalar value is used in an operation, it could be interpreted in three ways depending on the type of value the operation is expecting:

A scalar value will be interpreted as a number, if the operation is expecting a numeric value. If the scalar value is a numeric value, Perl will take it as is. If the scalar value is a string value, Perl will try to parse it into a number. If parsing failed, it will be interpreted as 0.
A scalar value will be interpreted as a string, if the operation is expecting a string value. If the scalar value is a string value, Perl will take it as is. If the scalar value is a numeric value, Perl will convert it into a string representation of that value.
A scalar value will be interpreted as TRUE or FALSE, if the operation is expecting a Boolean value. Perl will interpret number 0, string '0', and empty string '' as FALSE. Any other values will be interpreted as TRUE.

To verify the rules listed above, I wrote the following Perl tutorial script:

#- ScalarValue.pl
#- Copyright (c) HerongYang.com. All Rights Reserved.
#
   print(0.00, "\n");                  # 0
   print(00.00, "\n");                 # 00
   print(1e-1, "\n");                  # 0.1
   print(1e+50, "\n");                 # 1e+050
   print(1e+100, "\n");                # 1e+100
   print(1e+1000, "\n");               # 1.#INF
   print(1e+1000 + 1, "\n");           # 1.#INF
   print('1e+1000' + 1, "\n");         # 1.#INF
   print(0.1234567890123456789, "\n"); # 0.123456789012346
   print(1 / 3, "\n");                 # 0.333333333333333
   print(1 / '3', "\n");               # 0.333333333333333
   print(1 + 3, "\n");                 # 4
   print(1.3, "\n");                   # 1.3
   print(1 . 3, "\n");                 # 13
   print((1 . 3) * 5, "\n");           # 65
   print('Hello '. 'world!', "\n");    # Hello world!
   print(1 + 'a', "\n");               # 1
   print(1 * 'a', "\n");               # 0
   print(1 + '', "\n");                # 1
   print('FALSE', "\n") if (not 0);    # FALSE
   print('FALSE', "\n") if (not '0');  # FALSE
   print('FALSE', "\n") if (not '');   # FALSE
   print('TURE', "\n") if (' ');       # TURE
   print('TURE', "\n") if (1);         # TURE