I want to create a lexer/parser for a language that has non-delimited strings.
Which part of the language is a string is defined by the command preceding it.
For example it has statements that look like this:
pause 5
alert Hello world[CRLF] this contains 'pause' once (1)
Alert in this instance can end with any string, including keywords and numbers.
Further complicating things, the text can contain tags like [CRLF] that I want to separate too.
Ideally I'd want this to be broken up into:
[PAUSE][INT 5]
[ALERT][STR "Hello world"][CRLF][STR " this contains 'pause' once (1)"]
I'm currently using flex but from what I've gathered this kind of thing isn't possible with flex.
How can I achieve what I want here?
(Since one of your tags is "regex", I'll suggest a non-flex approach.)
From the example, it seems like you could just:
match each line against ^(\w+) (.+) to obtain command and arguments-text, and then
get individual arguments by splitting the arguments-text on (\[\w+\]) (assuming your regex library's split function can return both the splitter-strings and the split-strings).
It's possible your actual situation is more complex and something like flex makes more sense, but I'm not really seeing it so far.
Related
I am using den4b Renamer to rename a lot of files that follow a specific pattern. The program allows me to use RegEx: (https://www.den4b.com/wiki/ReNamer:Regular_Expressions)
I am stuck trying to conjure up an expression for a specific pattern.
My current RegEx:
Expression: ^(com\.)(([\w\s]*\.){0,4})([\w\s]*)$
Replace: \L$1\L$2\u$4
Note: \L and \u transform the sub-expression to upper and lower case as defined in the table below:
Here are a few example strings so you can get an idea of the input:
Android File Transfer.svg
Angular Console.svg
Au.Edu.Uq.Esys.Escript.svg
Avidemux.svg
Blackmagic Fusion8.svg
Broken Sword.svg
Browser360 Beta.svg
Btsync GUI.svg
Buttercup Desktop.svg
Calc.svg
Calibre EBook Edit.svg
Calibre Viewer.svg
Call Of Duty.svg
com.GitHub.Plugarut.Pwned Checker.svg
com.GitHub.Plugarut.Wingpanel Monitor.svg
com.GitHub.Rickybas.Date Countdown.svg
com.GitHub.Spheras.Desktopfolder.svg
com.GitHub.Themix Project.Oomox.svg
com.GitHub.Unrud.Remote Touchpad.svg
com.GitHub.Unrud.Video Downloader.svg
com.GitHub.Weclaw1.Image Roll.svg
com.GitHub.Zelikos.Rannum.svg
com.Gitlab.Miridyan.Mt.svg
com.Inventwithpython.Flippy.svg
com.Neatdecisions.Detwinner.svg
com.Rafaelmardojai.Share Preview.svg
com.Rafaelmardojai.Webfont Kit Generator.svg
Distributor Logo Antix.svg
Distributor Logo Archlabs.svg
Distributor Logo Dragonflybsd.svg
DOSBox.svg
Drawio.svg
Drweb GUI.svg
For this question I am focused on the strings that begin with com.xxx.xxx.
Since I can't only target those names in Renamer, the expression has to "play nice" with the other input file names and correctly leave them alone. That's why I've prefixed my expression with ^(com\.)
What I want:
Transform the entire string to lower case except for the last period separated part of the string.
Strip white space from the entire string.
For instance:
Original: com.GitHub.Alcadica.Develop.svg
After my Regex: com.github.alcadica.Develop.svg
What I want: com.github.alcadica.Develop.svg
This specific file is correctly renamed. What I'm having trouble with are names that have spaces in any part of the string. I can't figure out how to strip whitespace:
Original: com.Belmoussaoui.Read it Later.svg
After my Regex: com.belmoussaoui.Read it Later.svg
What I want: com.belmoussaoui.ReaditLater.svg
Here is a hypothetical example because I couldn't find a file with more than four parts. I want my pattern to be robust enough to handle this:
Original: com.Shatteredpixel.Another Level.Next.Pixel Dungeon.svg
After my Regex: com.shatteredpixel.another level.next.Pixel Dungeon.svg
What I want: com.shatteredpixel.anotherlevel.next.PixelDungeon.svg
Note that since I'm not using any kind of programming language, I don't have access to common string operations like trim, etc. I can, however, stack expressions. But this would create more overhead and since I am renaming thousands of files at a time I'd ideally like to keep it to one find/replace expression.
Any help would be greatly appreciated. Please let me know if I can provide any more information to make this more clear.
Edit:
I got it to work with the following rules:
Really inefficient, but it works. (Thanks to Jeremy in the comments for the idea)
I am using an Engineering Program which lets me Code formulas in order to filter out specific lines in a database. I am trying to look for a certain line in the database which contains e.g. "concrete" as a property.
In the Code I can use regular expressions.
The regex I was using so far looked like this:
".*(concrete).*";
so if the line in the database contains concrete, I will get the wanted result.
Now the Problem is: i would like to switch the word concrete with a variable, so that it Looks like this:
".*(#VARIABLE1).*";
(the Syntax with the # works in the program btw.)
the Problem is: if i set the variable as concrete, the program automatically switches it for 'concrete' . Obviously, the word concrete cant be found anymore, since the searchterm now contains the two ' Symbols in the beginning and i the end.
Is there a way to ignore those two characters using the Right regex?
what I want it to do is the following:
If a line in the database contains "25cm concrete in Grey"
I should get a match from the regex.
with the searchterm ".*(concrete).*"; it works, with the variable ".*(#VARIABLE1).*"; it doesnt.
EDIT:
the whole "Formula" in the program Looks like that:
if(Match(QTO(Typ:="Attribut{FloorsLayer_02_MaterialName}");".*(#V_QUALITY).*" ;"regex") ;QTO(Typ:="Attribut{Fläche}");0)
I want the if-condition to be true, when the match inside is true.
the whole QTO function is just the programs Syntax to use a certain Attribute into the match-function, the middle part is my Problem. I really don't know the programming language or anything,I'm new to this. hope it helps!
Thats more of a hack than a real solution and i'm not sure if it even works:
if you use the regex
.*(#VARIABLE1)?).*
and the string ?concrete(
this will result in a regex looking like this:
.*('?concrete(')?).*
which makes the additional characters optional.
This uses the following assumtption:
the string (#VARIABLE1) gets replaced by the ('<content of VARIABLE1>')
I am using the maven replacer plugin and I've run into a situation where I have a regular expression that matches across lines which I need to run on the input file until all matches have been replaced. The configuration for this expression looks like this:
<regexFlags>
<regexFlag>DOTALL</regexFlag>
</regexFlags>
<replacements>
<replacement>
<token>\#([^\n\r=\#]+)\#=([^\n\r]*)(.*)(\#default\.\1\#=[^\n\r]*)(.*)</token>
<value>#$1#=$2$3$5</value>
<replacement>
<replacements>
The input could look like this:
#d.e.f#=y
#a.b.c#=x
#h.i.j#=aaaa
#default.a.b.c#=QQQ
#asdfasd.fasdfs.asdfa#=23423
#default.h.i.j#=234
#default.RR.TT#=393993
and I want the output to look like this:
#d.e.f#=y
#a.b.c#=x
#h.i.j#=aaaa
#asdfasd.fasdfs.asdfa#=23423
#default.RR.TT#=393993
The intention is to re-write the file, but without the tokens with a #default prefix, where another token without the prefix has already been defined.
#default.a.b.c#=QQQ and #default.h.i.j#=234 have been removed from the output because other tokens already contains a.b.c and h.i.j.
The current problem I have is that the replacer plugin only replaces the first match, so my output looks like this:
#d.e.f#=y
#a.b.c#=x
#h.i.j#=aaaa
#asdfasd.fasdfs.asdfa#=23423
#default.h.i.j#=234
#default.RR.TT#=393993
Here, #default.a.b.c=QQQ is gone, which is correct, but #default.h.i.j#=234 is still present.
If I were writing this in code, I think I could probably just loop while attempting to match on the entire output, and break when there are no matches. Is there a way to do this with the replacer plugin?
Edit: I may have over simplified my example. A more realistic one is:
#d.e.f#=y
#a.b.c#=x
#h.i.j#=aaaa
#default.a.b.c#=QQQ
#asdfasd.fasdfs.asdfa#=23423
#default.h.i.j#=234
#default.RR.TT#=393993
#x.y.z#=0
#default.q.r.s#=1
#l.m.n#=8.3
#q.r.s#=78
#blah.blah.blah#=blah
This shows that it's possible for a default.x.x.x=y to precede a x.x.x=y token (as #default.q.r.s#=1 preceedes #q.r.s#=78`), my prior example wasn't clear about this. I do actually have an expression to capture this, it looks a bit like this:
\#default\.([^\n\r=#|]+)#=([^\n\r|]*)(.*)#\1#=([^\n\r|]*)(.*)
I know line separators are missing from this even though they were in the other one - I was experimenting with removing all line separators and treating it as a single line but that hasn't helped. I can resolve this problem simply by running each replacement multiple times by copying and pasting the configurations a few times, but that is not a good solution and will fail eventually.
I don't believe you could solve this problem as is, a work-around is to reverse the order of the file top to bottom, perform lookahead regex and then reverse the result order
pattern = #default\.(.*?)#[^\r\n]+(?=[\s\S]*#\1#) Demo
another way (depending on the capabilities of "Maven") is to run this pattern
#(.*)(#[\s\S]*)#default\.\1.*
and replace with #$1$2 Demo in a loop until there are no matches
then run this pattern
#default\.(.*)#.*(?=[\s\S]*\1)
and replace with nothing Demo in a loop until there are no matches
It doesn't look like the replacer plugin can actually do what I want. I got around this by using regular expressions to build multiple filter files, and then applying them to the resource files.
My original goal had been to use regular expressions to build a single, clean, and tidy filter file. In the end, I discovered that I was able to get away with just using multiple filters (not as clean or tidy) and apply them in the correct order.
Is there an easy way to generate a human-readable inflection list from Hunspell/Aspell dictionary data files?
For example, I'd like to generate the following outputs (for different languages):
...
book, books
book, books, booked, booking
...
go, goes, went, gone, going
...
I looked at the Hunspell/Aspell docs, but couldn't find an API call that would do this.
There is a method that the command line one does, but it doesn't output quite in the format you're looking for. You could also do this manually if you wanted though just by some simple scripting with regex.
The format of for each set of affixes is
TYPE TAG REMOVE REPLACE MATCH
Such that where TAG matches what follows what's behind the /in a given word in the .dicfile, you can do the following (presuming you've already stripped the word of the /...):
if($word =~ /$match$/) $word =~ s/$remove$/$replace/;
Notice the $ there matching the end-of-line/word. Adjust with ^ if it's a prefix.
There are three caveats:
The $match directly from the .aff file is in almost all cases equivalent to standard regex. There are minor variations such that if the match is something like [abc-gh], you'd be better to change it to (a|b|c|-|g|h) or [abcgh-] (hunspell doesn't use hyphen as a metacharacter) otherwise it'll be interpreted as [abcdefgh] (standard regex). For a negated character class, your options are to manually move the - to the end of the expression (e.g. [^a-df] to [^adf-] or to use negative look behinds.
If $replace is 0, then you should change it to an empty string.
If your result ends with /..., you need to reprocess it again because it has a double affix.
Be careful. By my rough calculations, the dictionary I'm working on could have more than 50 million words being formed (and I wouldn't be surprised if it hits beyond 100 million).
I recently discussed editors with a co-worker. He uses one of the less popular editors and I use another (I won't say which ones since it's not relevant and I want to avoid an editor flame war). I was saying that I didn't like his editor as much because it doesn't let you do find/replace with regular expressions.
He said he's never wanted to do that, which was surprising since it's something I find myself doing all the time. However, off the top of my head I wasn't able to come up with more than one or two examples. Can anyone here offer some examples of times when they've found regex find/replace useful in their editor? Here's what I've been able to come up with since then as examples of things that I've actually had to do:
Strip the beginning of a line off of every line in a file that looks like:
Line 25634 :
Line 632157 :
Taking a few dozen files with a standard header which is slightly different for each file and stripping the first 19 lines from all of them all at once.
Piping the result of a MySQL select statement into a text file, then removing all of the formatting junk and reformatting it as a Python dictionary for use in a simple script.
In a CSV file with no escaped commas, replace the first character of the 8th column of each row with a capital A.
Given a bunch of GDB stack traces with lines like
#3 0x080a6d61 in _mvl_set_req_done (req=0x82624a4, result=27158) at ../../mvl/src/mvl_serv.c:850
strip out everything from each line except the function names.
Does anyone else have any real-life examples? The next time this comes up, I'd like to be more prepared to list good examples of why this feature is useful.
Just last week, I used regex find/replace to convert a CSV file to an XML file.
Simple enough to do really, just chop up each field (luckily it didn't have any escaped commas) and push it back out with the appropriate tags in place of the commas.
Regex make it easy to replace whole words using word boundaries.
(\b\w+\b)
So you can replace unwanted words in your file without disturbing words like Scunthorpe
Yesterday I took a create table statement I made for an Oracle table and converted the fields to setString() method calls using JDBC and PreparedStatements. The table's field names were mapped to my class properties, so regex search and replace was the perfect fit.
Create Table text:
...
field_1 VARCHAR2(100) NULL,
field_2 VARCHAR2(10) NULL,
field_3 NUMBER(8) NULL,
field_4 VARCHAR2(100) NULL,
....
My Regex Search:
/([a-z_])+ .*?,?/
My Replacement:
pstmt.setString(1, \1);
The result:
...
pstmt.setString(1, field_1);
pstmt.setString(1, field_2);
pstmt.setString(1, field_3);
pstmt.setString(1, field_4);
....
I then went through and manually set the position int for each call and changed the method to setInt() (and others) where necessary, but that worked handy for me. I actually used it three or four times for similar field to method call conversions.
I like to use regexps to reformat lists of items like this:
int item1
double item2
to
public void item1(int item1){
}
public void item2(double item2){
}
This can be a big time saver.
I use it all the time when someone sends me a list of patient visit numbers in a column (say 100-200) and I need them in a '0000000444','000000004445' format. works wonders for me!
I also use it to pull out email addresses in an email. I send out group emails often and all the bounced returns come back in one email. So, I regex to pull them all out and then drop them into a string var to remove from the database.
I even wrote a little dialog prog to apply regex to my clipboard. It grabs the contents applies the regex and then loads it back into the clipboard.
One thing I use it for in web development all the time is stripping some text of its HTML tags. This might need to be done to sanitize user input for security, or for displaying a preview of a news article. For example, if you have an article with lots of HTML tags for formatting, you can't just do LEFT(article_text,100) + '...' (plus a "read more" link) and render that on a page at the risk of breaking the page by splitting apart an HTML tag.
Also, I've had to strip img tags in database records that link to images that no longer exist. And let's not forget web form validation. If you want to make a user has entered a correct email address (syntactically speaking) into a web form this is about the only way of checking it thoroughly.
I've just pasted a long character sequence into a string literal, and now I want to break it up into a concatenation of shorter string literals so it doesn't wrap. I also want it to be readable, so I want to break only after spaces. I select the whole string (minus the quotation marks) and do an in-selection-only replace-all with this regex:
/.{20,60} /
...and this replacement:
/$0"¶ + "/
...where the pilcrow is an actual newline, and the number of spaces varies from one incident to the next. Result:
String s = "I recently discussed editors with a co-worker. He uses one "
+ "of the less popular editors and I use another (I won't say "
+ "which ones since it's not relevant and I want to avoid an "
+ "editor flame war). I was saying that I didn't like his "
+ "editor as much because it doesn't let you do find/replace "
+ "with regular expressions.";
The first thing I do with any editor is try to figure out it's Regex oddities. I use it all the time. Nothing really crazy, but it's handy when you've got to copy/paste stuff between different types of text - SQL <-> PHP is the one I do most often - and you don't want to fart around making the same change 500 times.
Regex is very handy any time I am trying to replace a value that spans multiple lines. Or when I want to replace a value with something that contains a line break.
I also like that you can match things in a regular expression and not replace the full match using the $# syntax to output the portion of the match you want to maintain.
I agree with you on points 3, 4, and 5 but not necessarily points 1 and 2.
In some cases 1 and 2 are easier to achieve using a anonymous keyboard macro.
By this I mean doing the following:
Position the cursor on the first line
Start a keyboard macro recording
Modify the first line
Position the cursor on the next line
Stop record.
Now all that is needed to modify the next line is to repeat the macro.
I could live with out support for regex but could not live without anonymous keyboard macros.