How to reverse a string in Freemarker - freemarker

So simple question, which I simply cannot solve: how to reverse a string using Freemarker?
I have tried following:
<#assign reversed = mystring?reverse() />
But strings does not have reverse method... I've also tried:
<#assign reversed = mystring?split("")?reverse()?join("") />
But apparently split("") is not valid freemarker syntax. Is there a way to do this?


There's no function built in for reversing a string. Out of curiosity, what's the use case?
As of the trick with split, it's a valid syntax, only as the error message says, you aren't allowed to split with an empty string. But, you are allowed split with an empty regular expression:
<#assign reversed = myString?split("", "r")?reverse?join("")>
But this is a hack of course... Generally, you are supposed to expose the extra functions you need through TemplateMethodModelEx objects, or through Java beans, or even static utility classes.

Related

Length of Assign variable issue in freemarker

I am using freemarker ..want to find the length of assign variable ..i used size and length function ..but it fails and returns the error ..Please help me in how to find length of the assign variable
Please find the below code i have tried...
Input data --- cusID="a-1242" -- I want to split input data by - and want to store in separate variable through assign function
<#list (it.#CusID[0]!"")?split("-") as c><#if ((c?index) ==0)>
<#assign first>${c}</#assign>
<#assign firstlen = c?size>
</#if>
</#list>
Above code firstlen is used to find the length but it fails to find length
ERROR MESSAGES find below
For "?size" left-hand operand: Expected an extended-hash or sequence
or extended collection, but this has evaluated to a markup_output
(wrapper: f.c.TemplateXMLOutputModel):

As the error message says, first stores XML markup, not just a plain text string. You can't get the length of markup with ?length, as it's not obvious what that means (like if the content of which XML elements matter, what if you have an entity reference, etc.). The reason it's markup is that <#assign first>...</#assign> is not a normal assignment, it's for capturing output, and you are using XML output format. Instead, use normal value assignment: <#assign first = c>. Now first will have the same type as c, string.

What is the simplest way to get UTF-8 substring in Julia

UTF-8 string in Julia cannot use slice operator because it slice the byte index of string not character. For example
s = "ポケットモンスター"
s[1:4]
s[1:4] will be "ポケ" not "ポケット".
I would like to know the simplest and most readable for get UTF-8 sub-string in Julia.

Perhaps this question calls attention to some missing functions in the standard string library (which is supposed to undergo changes in the next version of Julia). In the meantime, if we define:
substr(s,i,j) = s[chr2ind(s,i):chr2ind(s,j)]
Then,
substr(s,1,4)
Would be "ポケット"

You might want to consider using UTF32String instead of UTF8String, if you are going to be doing this a lot, and only converting to UTF8String if necessary, when you are finished.

Freemarker string escaping doesn't work with default operator

We use Freemarker 2.3.20 and came across a strange behavior, when using the default operator together with string escaping like this:
${picture.#author[0]!""?js_string}
in this case, quotes in the authors value are not escaped if !"" is present.
We need to check first for the value and can't use the default op:
<#if picture.#author[0]??>${picture.#author[0]?js_string}</#if>
this is quite ugly and blown up code.
Is this a bug or a feature?

It's because of the operator precedences. ${picture.#author[0]!""?js_string} means ${picture.#author[0]!(""?js_string)}. What you want is ${(picture.#author[0]!"")?js_string}.

Regex can this be achieved

I'm too ambitious or is there a way do this
to add a string if not present ?
and
remove a the same string if present?
Do all of this using Regex and avoid the if else statement
Here an example
I have string
"admin,artist,location_manager,event_manager"
so can the substring location_manager be added or removed with regards to above conditions
basically I'm looking to avoid the if else statement and do all of this plainly in regex
"admin,artist,location_manager,event_manager".test(/some_regex/)
The some_regex will remove location_manager from the string if present else it will add it
Am I over over ambitions

You will need to use some sort of logic.
str += ',location_manager' unless str.gsub!(/location_manager,/,'')
I'm assuming that if it's not present you append it to the end of the string

Regex will not actually add or remove anything in any language that I am aware of. It is simply used to match. You must use some other language construct (a regex based replacement function for example) to achieve this functionality. It would probably help to mention your specific language so as to get help from those users.

Here's one kinda off-the-wall solution. It doesn't use regexes, but it also doesn't use any if/else statements either. It's more academic than production-worthy.
Assumptions: Your string is a comma-separated list of titles, and that these are a unique set (no duplicates), and that order doesn't matter:
titles = Set.new(str.split(','))
#=> #<Set: {"admin", "artist", "location_manager", "event_manager"}>
titles_to_toggle = ["location_manager"]
#=> ["location_manager"]
titles ^= titles_to_toggle
#=> #<Set: {"admin", "artist", "event_manager"}>
titles ^= titles_to_toggle
#=> #<Set: {"location_manager", "admin", "artist", "event_manager"}>
titles.to_a.join(",")
#=> "location_manager,admin,artist,event_manager"
All this assumes that you're using a string as a kind of set. If so, you should probably just use a set. If not, and you actually need string-manipulation functions to operate on it, there's probably no way around except for using if-else, or a variant, such as the ternary operator, or unless, or Bergi's answer
Also worth noting regarding regex as a solution: Make sure you consider the edge cases. If 'location_manager' is in the middle of the string, will you remove the extraneous comma? Will you handle removing commas correctly if it's at the beginning or the end of the string? Will you correctly add commas when it's added? For these reasons treating a set as a set or array instead of a string makes more sense.

No. Regex can only match/test whether "a string" is present (or not). Then, the function you've used can do something based on that result, for example replace can remove a match.
Yet, you want to do two actions (each can be done with regex), remove if present and add if not. You can't execute them sequentially, because they overlap - you need to execute either the one or the other. This is where if-else structures (or ternary operators) come into play, and they are required if there is no library/native function that contains them to do exactly this job. I doubt there is one in Ruby.
If you want to avoid the if-else-statement (for one-liners or expressions), you can use the ternary operator. Or, you can use a labda expression returning the correct value:
# kind of pseudo code
string.replace(/location,?|$/, function($0) return $0 ? "" : ",location" )
This matches the string "location" (with optional comma) or the string end, and replaces that with nothing if a match was found or the string ",location" otherwise. I'm sure you can adapt this to Ruby.

to remove something matching a pattern is really easy:
(admin,?|artist,?|location_manager,?|event_manager,?)
then choose the string to replace the match -in your case an empty string- and pass everything to the replace method.
The other operation you suggested was more difficult to achieve with regex only. Maybe someone knows a better answer

how do i cast an integer to a character in freemarker?

I am iterating over a list from 0-26, and would like to get the corresponding letter with each. For example, 0 will give me letter 'A' and so on.
I know that in java I can say:
char A = (char)65;
and that will give me an 'A' from my 65 integer.
But how can i do this on the front-end with freemarker, I have no clue?

Update: In FreeMarker 2.3.22 you can just use the (i + 1)?upper_abc expression. (The + 1 is needed if i is 0-based.)
Unfortunately, FreeMarker has no operator for that, yet. Although it's still possible to achieve this purely in FreeMarker by building a string literal that uses a \x escape and then ?eval it, that would be very ugly and inefficient. So the proper solution for now is to write your own TemplateMethodModelEx, and put it into #import-et utility library (if you have one) with <#assign numToChar = 'com.example.NumToCharMethod'?new()>, or add it as shared-variable in the Configuration.

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