是的,無關與正則表達式,它看起來像一個變量替換。
你說這是正式的定義?代入並看看指數符號後,看起來整個事物可以被修剪下來。此外,在那裏使用量詞會使無限多的數字。他們沒有考慮到任何地方的空間,也許它是對某個東西的嚴格分析。
[+-]?(([0-9]+ | ([0-9]*[\.][0-9]+) | ([0-9]+[\.][0-9]*)) [eE][+-]? [0-9]+)
[+-]? # '+' or '-' 0 or 1 time
( # group 1, not needed
( # group 2
[0-9]+ # a digit, 1 or more times
| # OR
( # group 3
[0-9]* # a digit, 0 or more times
[\.] # a '.' exactly 1 time, character class not needed
[0-9]+ # a digit, 1 or more times
) # end group 3
| # OR
( # group 4
[0-9]+ # a digit, 1 or more times
[\.] # a '.' exactly 1 time, character class not needed
[0-9]* # a digit, 0 or more times
) # end group 4
) # end group 2
[eE] # 'e' or 'E' exactly 1 time
[+-]? # '+' or '-' 0 or 1 time
[0-9]+ # a digit, 1 or more times
) # end group 1, not needed
來源
2011-02-05 19:39:07
sln
好簡單的解釋。謝謝。 – Bill 2011-02-05 20:44:21