使用Ruby比较字符串的开始或结束与子字符串的最快方法是什么？

Question

切分字符串"Hello world!"[0, 5] == 'Hello'是Ruby中常用的一种习惯用法，用于比较字符串的第一个或最后n个字符与另一个字符串。正则表达式也可以做到这一点。然后有和end_with?这也可以做到这一点。

我应该使用哪种速度？

Answer 1

考虑这些测试：

require 'fruity' 

STR = '!' + ('a'..'z').to_a.join # => "!abcdefghijklmnopqrstuvwxyz" 

结果的单个字符开始的字符串：

compare do 
    _slice { STR[0] == '!' } 
    _start_with { STR.start_with?('!') } 
    _regex { !!STR[/^!/] } 
end 

# >> Running each test 32768 times. Test will take about 1 second. 
# >> _start_with is faster than _slice by 2x ± 1.0 
# >> _slice is similar to _regex 

结果开始的字符串的多个字符：

compare do 
    _slice { STR[0..4] == '!abcd' } 
    _start_with { STR.start_with?('!abcd') } 
    _regex { !!STR[/^!abcd/] } 
end 

# >> Running each test 32768 times. Test will take about 2 seconds. 
# >> _start_with is faster than _slice by 2x ± 1.0 
# >> _slice is similar to _regex 

结果为单个字符结尾的字符：

个

compare do 
    _slice { STR[-1] == 'z' } 
    _end_with { STR.end_with?('z') } 
    _regex { !!STR[/z$/] } 
end 

# >> Running each test 32768 times. Test will take about 2 seconds. 
# >> _end_with is faster than _slice by 2x ± 1.0 
# >> _slice is faster than _regex by 2x ± 1.0 

结果结尾的字符串的多个字符：

compare do 
    _slice { STR[-5..-1] == 'vwxyz' } 
    _end_with { STR.end_with?('vwxyz') } 
    _regex { !!STR[/vwxyz$/] } 
end 

# >> Running each test 16384 times. Test will take about 1 second. 
# >> _end_with is faster than _slice by 2x ± 1.0 
# >> _slice is similar to _regex 

所以，清晰度和速度和end_with?应该是我们的第一选择。如果我们需要使用模式，那么切片或使用正则表达式是明显的选择。