Boolean values: Difference between revisions
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Everything else (including the number <code>0</code> and the empty string) is true. Constants <code>true</code> (and <code>TRUE</code>) exist. |
Everything else (including the number <code>0</code> and the empty string) is true. Constants <code>true</code> (and <code>TRUE</code>) exist. |
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<code>false</code>, <code>nil</code> and <code>true</code> are singleton instances of classes <code>FalseClass</code>, <code>NilClass</code> and <code>TrueClass</code> respectively. |
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Revision as of 18:32, 10 July 2009
You are encouraged to solve this task according to the task description, using any language you may know.
Show how to represent the boolean states "true" and "false" in a language. If other objects represent "true" or "false" in conditionals, note it.
BASIC
QuickBasic has no keywords for true and false. Boolean expressions evaluate to 0 when false, and a non-zero value when true. Numbers also work in place of boolean expressions following those rules.
Java
Java has true and false keywords. There are also object wrappers Boolean.TRUE and Boolean.FALSE which act in the same places, but have methods defined for them.
Python
The values in Python that are false are: False, None, 0 (including 0 of all numeric types, and any object whose .__nonzero__() method returns false), and empty containers (including empty strings, lists, tuples, dictionaries, sets, etc., and any object whose .__len__() method returns 0).
Everything else is true. Constant True exists.
Ruby
The only values in Ruby that are false are: false and nil. They have synonyms FALSE and NIL.
Everything else (including the number 0 and the empty string) is true. Constants true (and TRUE) exist.
false, nil and true are singleton instances of classes FalseClass, NilClass and TrueClass respectively.