Module 07 - Regular Expressions
Lesson 03 - Regex Functions
Now, to make use of all of these expressions you can write, YAYA has a few more functions. We’ve already covered RE_MATCH, which searches for an exact match to the regular expression, and RE_SEARCH, which searches for a partial match. There is also RE_GREP, which searches for all of the matches in a string, and outputs the count of matches.
OnReGrep
{
_expression = "th"
_string = "the most important thing is to breathe"
RE_GREP(_string,_expression)
}
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The above function will output 3, since “th” appears in the target string three times.
RE_GREP is the last of the string searching functions. After that, there are RE_REPLACE and RE_SPLIT, which are regex versions of REPLACE and SPLIT.
OnReReplace
{
_expression = "colou?r"
_string = "My favorite color is purple"
RE_REPLACE(_string,_expression,"hue")
}
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The above function will output the string My favorite hue is purple
There is also RE_REPLACEEX, which is like RE_REPLACE, except metacharacters can be included in the replacement string.
All of the regex functions we have covered thus far, including RE_MATCH and RE_SEARCH, have a special property. When executed, they will save some additional data about any matches that were found. This data is retrievable using the functions RE_GETSTR, RE_GETPOS, and RE_GETLEN.
RE_GETSTR will return an array of the substrings that were matched by the regular expression. Element 0 will be the entire match, and each element after that will be what was contained in each capture group. So if you had 3 capture groups, RE_GETSTR[1] would be the result of the first capture group, RE_GETSTR[2] would be the result of the second capture group, and RE_GETSTR[3] would be the result of the third capture group.
OnReGetString
{
_expression = "(favou?rite) (colou?r)"
_string = "My favorite color is purple"
void RE_SEARCH(_string,_expression)
RE_GETSTR[1]
}
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The above function will output favorite
Next is RE_GETPOS. RE_GETPOS will return an array of the starting positions for each capture group that matched. Note that these are 0-indexed, so if it matched at the start of the string, the output would be 0.
This is similar to RE_GETSTR; element 0 will be the position where the whole expression matched, and each element after will be for each individual capture group.
OnReGetPosition
{
_expression = "(favou?rite) (colou?r)"
_string = "My favorite color is purple"
void RE_SEARCH(_string,_expression)
RE_GETPOS[2]
}
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The above function will output 12, which is the position in the string where the word “color” (the second capture group) begins.
Finally, there is RE_GETLEN. This will return an array of the string lengths of each captured segment. As with the others, element 0 is for the whole match, and each element after is for each capture group.
OnReGetLength
{
_expression = "(favou?rite) (colou?r)"
_string = "My favorite color is purple"
void RE_SEARCH(_string,_expression)
RE_GETLEN[2]
}
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The above function will output 5, since it matched with “color”, which is 5 characters long.
Note that if you are using RE_REPLACE, RE_REPLACEEX, or RE_SPLIT, these three functions will only have element 0, as there is no other data to store.
Three functions left to go. The following functions do not use RE_GETSTR, RE_GETPOS, and RE_GETLEN.
RE_ASEARCH is like ASEARCH, and RE_ASEARCHEX is like ASEARCHEX. They take an argument for the expression you want to use to search, and an argument of the array to search in. Note that, unlike ASEARCH and ASEARCHEX, these will find partial matches too, not just perfect matches. RE_ASEARCH will return the index number for the first match it finds, while RE_ASEARCHEX will return an array of all the indices for the matches it finds.
OnReArraySearch
{
_colors = ("red","orange","yellow","green","cyan","blue","purple","magenta")
_expression = "a"
RE_ASEARCHEX(_expression,_colors)
}
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The above function will output 1,4,7, the positions of “orange”, “cyan”, and “magenta”, since these all have an “a” in them.
Finally, there is RE_OPTION. RE_OPTION lets you set options for your regular expressions, much like how you can set options in PERL. It takes a single argument, which is the option you want to set.
i makes the expression case-insensitive. m treats the expression as multiple lines. s makes the . (wildcard) character also match newlines. x ignores comments (which can be written starting with #) and whitespace in regular expressions.
The default option is m. You can specify multiple options at once, such as mxi, or si.
If you omit the argument, the current option will be returned instead. Otherwise, it will return the options you have just set.
OnReOption
{
_expression = "colou?r"
_string = "COLOR"
void RE_OPTION("i")
RE_MATCH(_string,_expression)
}
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The above function will output 1
Further Context
We did it! That’s all I’m going to show you about regex. And I’ll be honest with you, I have never in my life used that RE_OPTION function except when testing it for this guide, so if you don’t get it I wouldn’t even worry about it. You can play with it if you ever get really into regex and find you need it.