使用Ruby比較字符串的開始或結束與子字符串的最快方法是什麼？

Question

切分字符串"Hello world!"[0, 5] == 'Hello'是Ruby中常用的一種習慣用法，用於比較字符串的第一個或最後n個字符與另一個字符串。正則表達式也可以做到這一點。然後有和end_with?這也可以做到這一點。

我應該使用哪種速度？

Answer 1

考慮這些測試：

require 'fruity' 

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

結果的單個字符開始的字符串：

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 

結果開始的字符串的多個字符：

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 

結果爲單個字符結尾的字符：

個

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 

結果結尾的字符串的多個字符：

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?應該是我們的第一選擇。如果我們需要使用模式，那麼切片或使用正則表達式是明顯的選擇。