创建匹配数字范围的正则表达式的函数
我正在使用 Amazon Mechanical Turk API,它只允许我使用正则表达式来过滤数据字段.
I am working with the Amazon Mechanical Turk API and it will only allow me to use regular expressions to filter a field of data.
我想向函数输入一个整数范围,例如 256-311 或 45-1233,并返回一个仅匹配该范围的正则表达式.
I would like to input an integer range to a function, such as 256-311 or 45-1233, and return a regex that would match only that range.
匹配 256-321 的正则表达式将是:
A regex matching 256-321 would be:
((25[6-9])|(2[6-9][0-9])|(3[0-1][0-9])|(32[0-1]))
这部分相当简单,但我在创建这个正则表达式的循环时遇到了麻烦.
That part is fairly easy, but I am having trouble with the loop to create this regex.
我正在尝试构建一个这样定义的函数:
I am trying to build a function defined like this:
function getRangeRegex( int fromInt, int toInt)
{
return regexString;
}
我浏览了整个网络,我很惊讶过去似乎没有人解决过这个问题.这是一个难题……
I looked all over the web and I am surprised that it doesn't look like anyone has solved this in the past. It is a difficult problem...
感谢您的宝贵时间.
推荐答案
这里有一个快速破解:
<?php
function regex_range($from, $to) {
if($from < 0 || $to < 0) {
throw new Exception("Negative values not supported");
}
if($from > $to) {
throw new Exception("Invalid range $from..$to, from > to");
}
$ranges = array($from);
$increment = 1;
$next = $from;
$higher = true;
while(true) {
$next += $increment;
if($next + $increment > $to) {
if($next <= $to) {
$ranges[] = $next;
}
$increment /= 10;
$higher = false;
}
else if($next % ($increment*10) === 0) {
$ranges[] = $next;
$increment = $higher ? $increment*10 : $increment/10;
}
if(!$higher && $increment < 10) {
break;
}
}
$ranges[] = $to + 1;
$regex = '/^(?:';
for($i = 0; $i < sizeof($ranges) - 1; $i++) {
$str_from = (string)($ranges[$i]);
$str_to = (string)($ranges[$i + 1] - 1);
for($j = 0; $j < strlen($str_from); $j++) {
if($str_from[$j] == $str_to[$j]) {
$regex .= $str_from[$j];
}
else {
$regex .= "[" . $str_from[$j] . "-" . $str_to[$j] . "]";
}
}
$regex .= "|";
}
return substr($regex, 0, strlen($regex)-1) . ')$/';
}
function test($from, $to) {
try {
printf("%-10s %s
", $from . '-' . $to, regex_range($from, $to));
} catch (Exception $e) {
echo $e->getMessage() . "
";
}
}
test(2, 8);
test(5, 35);
test(5, 100);
test(12, 1234);
test(123, 123);
test(256, 321);
test(256, 257);
test(180, 195);
test(2,1);
test(-2,4);
?>
产生:
2-8 /^(?:[2-7]|8)$/
5-35 /^(?:[5-9]|[1-2][0-9]|3[0-5])$/
5-100 /^(?:[5-9]|[1-9][0-9]|100)$/
12-1234 /^(?:1[2-9]|[2-9][0-9]|[1-9][0-9][0-9]|1[0-2][0-3][0-4])$/
123-123 /^(?:123)$/
256-321 /^(?:25[6-9]|2[6-9][0-9]|3[0-2][0-1])$/
256-257 /^(?:256|257)$/
180-195 /^(?:18[0-9]|19[0-5])$/
Invalid range 2..1, from > to
Negative values not supported
未经适当测试,使用风险自负!
Not properly tested, use at your own risk!
是的,生成的正则表达式在许多情况下可以写得更紧凑,但我把它留给读者作为练习:)
And yes, the generated regex could be written more compact in many cases, but I leave that as an exercise for the reader :)
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