《guide to ruby》读书笔记1

1、ruby有三种变量：

Global variables can be used anywhere in your program. They never go out of sight.以$开头

Instance variables，以@开头

Class variables，以@@开头

2、布尔值

The?unless?keyword has a policy of?only allowing those with a negative charge in. Who are:?nil?and?false.

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And another nice trick: stack the?if?and?unless.
This trick is a gorgeous way of expressing,?Do this only if?a* is true and *b?isn’t true.
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3、循环
When you are iterating through a list, you may use?next?toskip on to the next item
case year when 1894   "Born." when 1895..1913   "Childhood in Lousville, Winston Co., Mississippi." else   "No information about this year." endif 1894 === year   "Born." elsif 1895..1913 === year   "Childhood in Lousville, Winston Co., Mississippi." else   "No information about this year." end
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Take the Ranges above.?(1895..1913)?isn’t at all?equal?to?1905. No, the Range?(1895..1913)?is only truly?equal?to any other Range?(1895..1913).