編碼默認到ASCII-8BIT

Question

我有以下文件：

# encoding: UTF-8 
a = 1 << 7 
puts a.chr.encoding 

這讓我回ASCII-8BIT。爲什麼這不會退回UTF-8我期望？

Answer 1

chr具有編碼參數，默認爲US-ASCII，當炭是< 0x80和ASCII-8BIT爲< 0xff（有UTF是相同的ASCII）：

65.chr.encoding     # => #<Encoding:US-ASCII> 
128.chr.encoding     # => #<Encoding:ASCII-8BIT> 
255.chr.encoding     # => #<Encoding:ASCII-8BIT> 
256.chr.encoding     # => RangeError: 256 out of char range 

Encoding.default_internal = Encoding::UTF_8 
65.chr.encoding     # => #<Encoding:US-ASCII> 
255.chr.encoding     # => #<Encoding:ASCII-8BIT> 
256.chr.encoding     # => #<Encoding:UTF-8> 

65.chr(Encoding::UTF_8).encoding # => #<Encoding:UTF-8> 
128.chr(Encoding::UTF_8).encoding # => #<Encoding:UTF-8> 
500.chr(Encoding::UTF_8).encoding # => #<Encoding:UTF-8>