There are strings in that view:
2[a]2[ab]
3[a]2[r2[t]]
a2[aa3[b]]
Digits means count of repeat string inside brackets. So decoding string will be:
aaabab
aaarttrtt
aaabbbaabbb
I need an algorithm of decoding string, preferable on Java
There is a simple solution with recursion. Just take symbol by symbol, and as soon as we meet the digit - it means begin of packed string. Call method unpacked, where inside call unpacked again on next digit appeareance.
Related
I have this:
function dec2hex(IN)
local OUT
OUT = string.format("%x",IN)
return OUT
end
and need IN to have padded zeros to string length of 6.
I can't use String.Utils or PadLeft. It's within an app called Watchmaker which uses a cut down version of Lua.
String formats in Lua work mostly just like in C. So to pad a number with zeros, just use %0n where n is the number of places. For example
print(string.format("%06x", 16^4-1))
will print 00ffff.
See chapter 20 The String Library of “Programming in Lua”, the reference of string.format, and the C reference for the printf family of functions for details.
If you store your format string locally you can call the format method on to the format string and the example of #Henri results in ("%06x"):format(0xffff)
print(("%06x"):format(0xffff)) -- Prints `00ffff`
You can write numbers in hex format. It is the same as C.
Trying to make a textfield where people write the unicode without the backslash. I want to add the backslash after they typed it. So the user types u2605 and the code converts it to "\u2605", i then convert this to a unicode character and insert it in textflow.
My code:
this works:
span.text = publicFunctions.htmlUnescape(he.encode("\u2605"))
this doesn't work:
span.text = publicFunctions.htmlUnescape(he.encode("\\u"+"2605"))
how to make a string that acts as a unicode string?
Tried all sorts of things, escape(unescape()), convert to number, "\u", "\u" ... nothing helps.
trace("\u2605" == "\u"+"2605") ... will return false. So will
trace("\u2605" == "\u"+"2605")
"\u2605" is a string with a single character, the character with the code point 2605, while "\\u" + "2605" is a string with 6 characters (the backslash, the u and the four digit number).
If you want to construct a unicode character from just the four digits, you should be able to use String.fromCharCode. The thing is just that the escape sequence uses a hexadecimal number, while the method obviously takes a decimal number. So if the user enters a hexadecimal string, you will have to convert that first:
trace(String.fromCharCode(parseInt('2605', 16)) == '\u2605'));
That's an interesting issue! I don't think you can concatenate a string literal and achieve what you're trying to do. The relevant character escaping happens when the string literal is originally formed, which means that you need the whole sequence together in the first place.
But you should be able to take the user-supplied number and dynamically generate a Unicode string with String.fromCharCode(...).
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/String.html#fromCharCode()
I am trying to finish up a homework assignment, and am down to the last part. First, I'll show you the type that I am dealing with:
TYPE Book_Collection IS
RECORD
Books : Book_Collection_Array;
Max_Size : Integer;
Size : Integer;
END RECORD;
TYPE Book_Type IS
RECORD
Title,
Author,
Publisher : Title_Str;
Year : Year_Type;
Edition : Natural;
Isbn : Isbn_Type;
Price : Dollars;
Stock : Natural;
Format : Format_Type;
END RECORD;
Book_Collection_Array is an array of book_type. These are private types, so the array is bounded (1..200).
There is a function called ToString in a separate package that was provided to us, that takes a book_type as input, and returns a string of all the elements of book_type. What I need to create is a function that takes book_collection is a parameter, and returns a string concatenating all of the strings that are returned by the ToString function that was provided, for the book_types that exist in that book_collection. I have made multiple attempts, but am constantly getting range check failures. Can anyone point me in the right direction?
*Edit:
Thank you to both of you for your help. I went the route of using an unbounded string, and appending each string to it, then declaring an output string and setting it as a constant string equal to the the To_String of the unbounded_string.*
I'll give you a hint.
Ada strings ideally aren't treated or handled much like C or Java strings at all. C strings count on a trailing nul (0) character to designate the end of data in a buffer. Java strings keep track of their own length, and will dynamically reallocate themselves to keep to the proper length if need be. So typical string-handling idioms in those languages think nothing of progressively modifying a string variable.
Ada strings instead are expected to be perfectly-sized when created. Most routines will assume that every element in a string array contains valid character data, and any destination string you assign data into will be perfectly sized to hold it. If that isn't the case, usually an exception is raised (and most likely your program crashes).
There are several ways to deal with this when you are building a string. One way is to create a really big string object as a buffer, and keep a separate length variable to tell your code how much data is really in there at all times. Then when you call Ada string routines you can feed them just the slice of data from the string that is valid. eg: Put_line (My_New_String(1..My_String_Length));
A better way is to just deal with perfectly-sized constant strings. For example, if you want to tack String1 and String2 together, the safe Ada way to do this is:
My_New_String : constant String := String1 & String2;
Then if you later want a string that is this string with String3 tacked on:
My_New_New_String : constant String := My_New_String & String3;
For more info on this, I suggest you look at some of the links over on the right side of this browser window under the heading "Related". I see a lot of good stuff in there.
Is there any way to replace a character at position N in a string in Lua.
This is what I've come up with so far:
function replace_char(pos, str, r)
return str:sub(pos, pos - 1) .. r .. str:sub(pos + 1, str:len())
end
str = replace_char(2, "aaaaaa", "X")
print(str)
I can't use gsub either as that would replace every capture, not just the capture at position N.
Strings in Lua are immutable. That means, that any solution that replaces text in a string must end up constructing a new string with the desired content. For the specific case of replacing a single character with some other content, you will need to split the original string into a prefix part and a postfix part, and concatenate them back together around the new content.
This variation on your code:
function replace_char(pos, str, r)
return str:sub(1, pos-1) .. r .. str:sub(pos+1)
end
is the most direct translation to straightforward Lua. It is probably fast enough for most purposes. I've fixed the bug that the prefix should be the first pos-1 chars, and taken advantage of the fact that if the last argument to string.sub is missing it is assumed to be -1 which is equivalent to the end of the string.
But do note that it creates a number of temporary strings that will hang around in the string store until garbage collection eats them. The temporaries for the prefix and postfix can't be avoided in any solution. But this also has to create a temporary for the first .. operator to be consumed by the second.
It is possible that one of two alternate approaches could be faster. The first is the solution offered by Paŭlo Ebermann, but with one small tweak:
function replace_char2(pos, str, r)
return ("%s%s%s"):format(str:sub(1,pos-1), r, str:sub(pos+1))
end
This uses string.format to do the assembly of the result in the hopes that it can guess the final buffer size without needing extra temporary objects.
But do beware that string.format is likely to have issues with any \0 characters in any string that it passes through its %s format. Specifically, since it is implemented in terms of standard C's sprintf() function, it would be reasonable to expect it to terminate the substituted string at the first occurrence of \0. (Noted by user Delusional Logic in a comment.)
A third alternative that comes to mind is this:
function replace_char3(pos, str, r)
return table.concat{str:sub(1,pos-1), r, str:sub(pos+1)}
end
table.concat efficiently concatenates a list of strings into a final result. It has an optional second argument which is text to insert between the strings, which defaults to "" which suits our purpose here.
My guess is that unless your strings are huge and you do this substitution frequently, you won't see any practical performance differences between these methods. However, I've been surprised before, so profile your application to verify there is a bottleneck, and benchmark potential solutions carefully.
You should use pos inside your function instead of literal 1 and 3, but apart from this it looks good. Since Lua strings are immutable you can't really do much better than this.
Maybe
"%s%s%s":format(str:sub(1,pos-1), r, str:sub(pos+1, str:len())
is more efficient than the .. operator, but I doubt it - if it turns out to be a bottleneck, measure it (and then decide to implement this replacement function in C).
With luajit, you can use the FFI library to cast the string to a list of unsigned charts:
local ffi = require 'ffi'
txt = 'test'
ptr = ffi.cast('uint8_t*', txt)
ptr[1] = string.byte('o')
I've a question about Fortran 77 and I've not been able to find a solution.
I'm trying to store an array of strings defined as the following:
character matname(255)*255
Which is an array of 255 strings of length 255.
Later I read the list of names from a file and I set the content of the array like this:
matname(matcount) = mname
EDIT: Actually mname value is hardcoded as mname = 'AIR' of type character*255, it is a parameter of a function matadd() which executes the previous line. But this is only for testing, in the future it will be read from a file.
Later on I want to print it with:
write(*,*) matname(matidx)
But it seems to print all the 255 characters, it prints the string I assigned and a lot of garbage.
So that is my question, how can I know the length of the string stored?
Should I have another array with all the lengths?
And how can I know the length of the string read?
Thanks.
You can use this function to get the length (without blank tail)
integer function strlen(st)
integer i
character st*(*)
i = len(st)
do while (st(i:i) .eq. ' ')
i = i - 1
enddo
strlen = i
return
end
Got from here: http://www.ibiblio.org/pub/languages/fortran/ch2-13.html
PS: When you say: matname(matidx) it gets the whole string(256) chars... so that is your string plus blanks or garbage
The function Timotei posted will give you the length of the string as long as the part of the string you are interested in only contains spaces, which, if you are assigning the values in the program should be true as FORTRAN is supposed to initialize the variables to be empty and for characters that means a space.
However, if you are reading in from a file you might pick up other control characters at the end of the lines (particularly carriage return and/or line feed characters, \r and/or \n depending on your OS). You should also toss those out in the function to get the correct string length. Otherwise you could get some funny print statements as those characters are printed as well.
Here is my version of the function that checks for alternate white space characters at the end besides spaces.
function strlen(st)
integer i,strlen
character st*(*)
i = len(st)
do while ((st(i:i).eq.' ').or.(st(i:i).eq.'\r').or.
+ (st(i:i).eq.'\n').or.(st(i:i).eq.'\t'))
i = i - 1
enddo
strlen = i
return
end
If there are other characters in the "garbage" section this still won't work completely.
Assuming that it does work for your data, however, you can then change your write statement to look like this:
write(*,*) matname(matidx)(1:strlen(matname(matidx)))
and it will print out just the actual string.
As to whether or not you should use another array to hold the lengths of the string, that is up to you. the strlen() function is O(n) whereas looking up the length in a table is O(1). If you find yourself computing the lengths of these static strings often, it may improve performance to compute the length once when they are read in, store them in an array and look them up if you need them. However, if you don't notice the slowdown, I wouldn't worry about it.
Depending on the compiler that you are using, you may be able to use the trim() intrinsic function to remove any leading/trailing spaces from a string, then process it as you normally would, i.e.
character(len=25) :: my_string
my_string = 'AIR'
write (*,*) ':', trim(my_string), ':'
should print :AIR:.
Edit:
Better yet, it looks like there is a len_trim() function that returns the length of a string after it has been trimmed.
intel and Compaq Visual Fortran have the intrinsic function LEN_TRIM(STRING) which returns the length without trailing blanks or spaces.
If you want to suppress leading blanks or spaces, use "Adjust Left" i.e. ADJUSTF(STRING)
In these FORTRANs I also note a useful feature: If you pass a string in to a function or subroutine as an argument, and inside the subroutine it is declared as CHARACTER*(*), then
using the LEN(STRING) function in the subroutine retruns the actual string length passed in, and not the length of the string as declared in the calling program.
Example:
CHARACTER*1000 STRING
.
.
CALL SUBNAM(STRING(1:72)
SUBROUTINE SYBNAM(STRING)
CHARACTER*(*) STRING
LEN(STRING) will be 72, not 1000