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   ► KBWebsite Scri...PerlBeginners Co...   Print This     
  From the January 2016 Issue of Prestwood eMag
 
Perl Beginners Corner:
Perl Literals (quote)
 
Posted 11 years ago on 11/6/2008 and updated 1/29/2009
Perl Code Snippet:
 A flashcard from our Perl Flashcards Library
 A code snippet from our Perl Code Snippets Page
 Tags: Perl , Literals

KB101543



General Info: Programming Literals

A value directly written into the source code of a computer program (as opposed to an identifier like a variable or constant). Literals cannot be changed. Common types of literals include string literals, floating point literals, integer literals, and hexidemal literals. Literal strings are usually either quoted (") or use an apostrophe (') which is often referred to as a single quote. Sometimes quotes are inaccurately referred to as double quotes.

Languages Focus: Literals

In addition to understanding whether to use a quote or apostrophe for string literals, you also want to know how to specify and work with other types of literals including floating point literals. Some compilers allow leading and trailing decimals (.1 + .1), while some require a leading or trailing 0 as in (0.1 + 0.1). Also, because floating point literals are difficult for compilers to represent accurately, you need to understand how the compiler handles them and how to use rounding and trimming commands correctly for the nature of the project your are coding.

Perl Literals

String literals are quoted as in "Prestwood". If you need to embed a quote use a slash in front of the quote as in \".

To specify a floating point literal between 1 and -1, you can preceed the decimal with a 0 or not (both work). In other words, preceding and following decimals are allowed (both .1 and 0.1). Trailing decimals are also allowed (1, 1., and 1.0 are all equivalent and allowed).

Syntax Example:
print "Hello";
print "Hello \"Mike\".";
  
#Does Perl evaluate this simple
#floating point math correctly? No! 
if ((.1 + .1 + .1) == .3) {
  print("Correct");
} else {
  print("Not correct");
}

Working Example

#!/usr/local/bin/perl -w
print("Content-type: text/html\n\n");
#Start of HTML page.
print("<html>");
print("<head><title>Perl Literals</title></head>");
print("<body>");

if ((.1 + .1 + .1) == .3) {
 print("Correct");
} else {
  print("Not correct");
}

#Trailing decimals.
if ((1.0 + 1. + 1) == 3) {
 print("Correct");
} else {
  print("Not correct");
}
print("</body></html>");

More Info

Definition:  Programming Literals

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Code Contributed By Mike Prestwood:

Mike Prestwood is a drummer, an author, and creator of the PrestwoodBoards online community. He is the President & CEO of Prestwood IT Solutions. Prestwood IT provides Coding, Website, and Computer Tech services. Mike has authored 6 computer books and over 1,200 articles. As a drummer, he maintains play-drums.com and has authored 3 drum books. If you have a project you wish to discuss with Mike, you can send him a private message through his PrestwoodBoards home page or call him 9AM to 4PM PST at 916-726-5675 x205.

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