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Learn Red ? Fundamentals of Red
book

Learn Red ? Fundamentals of Red

by Ivo Balbaert
May 2018
Beginner content levelBeginner
252 pages
6h 19m
English
Packt Publishing
Content preview from Learn Red ? Fundamentals of Red

if  

Here is how if works:

  • When a condition is true, then evaluate the block of code that follows
  • If the condition is false, do nothing; more precisely, the none value is returned:
;-- see Chapter04/conditions.red:account: -250if account < 0 [print "Your account is overdrawn."] ;== Your account is overdrawn.if now/time < 12:00 [print "before noon"]           ;== before noon, if e.g. 10:53

The condition (here, account < 0 or now/time < 12:00) need not be enclosed in ( ), but the code following it must be in a block []

Logical operations such as and, or, and not can be used to create composite conditions. For instance, here we use not to test whether a file is present, using the exists? function:

if not exists? %missing.txt [print "File missing.txt ...
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Publisher Resources

ISBN: 9781789130706Supplemental Content