2014-11-08 21:10

# php简单的正则表达式搜索和替换和随机子串

i have a string to be used for latex later the string is... roughly

$string = "\\sin\\left(x\ight)^{2}";  where the sin could also be cos, tan, sec, log, etc.. the exponent could also be any integer, float or variable, the argument could be anything.. I would like a regex function that turns it into $string  = "\\sin^{2}\\left(x\ight)";


or more generally

generalstring = "f(t)^{n}";


to be turned into "f^{n}(t)"; my apologies in advance, i have a feeling this should be extremely easy to do, I'm just learning this.

oh also i would like to restric this to only strings with trig functions logs and some other ones where my functions are not printing correctly.

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#### 2条回答

• douxie9471 7年前

$string = preg_replace('/\\\$$\w+)\\\\left\\((.+?)\\\ight\$$\\^\\{([^}]+)\\}/','\\\\$1^{$3}\left($2ight)',$string);  For me, the output is: print "$string
";

\sin^{2}\left(xight)


Another test:

$string = "\\cos\\left(3x\ight)^{2.6}";  Output: \cos^{2.6}\left(3xight)  It also works for multiple functions, since preg_replace is global per default. $string = "\\sin\\left(x\ight)^{3}\\cos\\left(y\ight)^{2}";

\sin^{3}\left(xight)\cos^{2}\left(yight)


Edit: Please note the corrected expression.

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• dtujfmfs06058 7年前

A regex like

(\\{2}sin|cos|tan|sec|log)([^^]*)(\^\{[^}]*\})


see how the regex matches http://regex101.com/r/iW4pZ3/1

The replacement string is \\1\\3\\2

preg_replace("/(\\\\{2}sin|cos|tan|sec|log)([^^]*)(\\^\\{[^}]*\\})/","\\1\\3\\2","\\\\sin\\\\left(x\\\ight)^{2}");


would produce an output as

\\sin^{2}\\left(x\ight)

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