|Write a program to reverse a string in perl||The above code snippet also works fine. What I mean is that, with the following code piece for Borodin Borodin k 9 9 gold badges 66 66 silver badges bronze badges. Also see shiftunshift and push. As if reverse had no impact. Improve this question.|
|Professional thesis statement ghostwriting service uk||Iustus alius egestas vitae, eros Piratica. When you ask the Monks to do your homework, it's well to make note of that fact in your initial post. So we only have two cases: reversing a scalar and reversing an array. How is it that the print inside the for loop is changing the behavior of string reversal? Every version of perl has it. Prev Next. Gabor can help refactor your old Perl code-base.|
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So we only have two cases: reversing a scalar and reversing an array. This is nice, but it also has some pitfalls. The pitfalls The two behaviors of reverse are not decided by its parameter, but by the construct that is on the left hand side. As if reverse had no impact. What about this one? Did the reverse not work there, or were the words already reversed? As if reverse has not impact. Indeed, if you try to reverse a string the result of join in this case , but put the call in LIST context created by the say function, then it tries to reverse the list given to it string-by-string.
Semordnilap BTW words like "stressed" and "desserts" are called Semordnilap. They are a a strange form of Palindrome where the reversed version of a word has a different, but valid meaning. Conclusion Remember, the behavior of reverse depends on its context. On what is on its left-hand side. Toggle navigation Perl Maven. Standard output, standard error and command line redirection Warning when something goes wrong What does die do?
Unknown warnings category Can't use string Recursion is not an optimal approach here, since the number of recursive calls will match the length of the string, and each call added to the call-stack has a cost. Also, the regexp contortion as a means of eliminating any "built-in" functions ie, substr does nothing to dispel the rumor that Perl is difficult to read. I'm always tempted to write recursion like this:. Which is the same thing but more explicit, and possibly more readable and possibly less, since we've lost variable names that look like strings.
Toady Tim. Is map a function, technically? Back to Seekers of Perl Wisdom. Replies are listed 'Best First'. CountZero A program should be light and agile, its subroutines connected like a string of pearls. Original string: ab Using function: ab Using reverse: ba Original string: abcd Using function: dbca Using reverse: dcba. If you didn't program your executable by toggling in binary, it wasn't really programming!
End case. PerlMonks parthenogenetically spawned by Tim Vroom. PerlMonks is a proud member of the The Perl Foundation. Is your data what you think it is? Need Help?? In Perl, a string is not an array of characters as in C. What is wrong with using the available tools and functions?
Unless this is homework, it is a silly requirement. Iustus alius egestas vitae, eros Piratica,. Hello, your Perl solution seems to have problems with strings that have an even number of characters: Original string: ab Using function: ab Using reverse: ba Original string: abcd Using function: dbca Using reverse: dcba [download] Excellence is an art won by training and habituation: we do not act rightly because we have virtue or excellence, but we rather have these because we have acted rightly.
I don't know how old this thread is but I found it interesting to practice manipulation for strings, please keep in mind that I am but a few weeks into this perl code but did I meet the requirements? Also see shift , unshift and push -stevieb. Otherwise, someone with a spark of evil might just post code to do the job with such sophistication that your instructor will immediately know you've been cheating.
No built-in functions abundant use of Perl's operators, though. Super Search where title contains all of "reverse", "string". Log In?
Such a calculation is an important part of many bioinformatics applications. For instance, when searching a database with some query DNA, it is common to automatically search for the reverse complement of the query as well, since you may have in hand the opposite strand of some known gene. Without further ado, here's Example , which uses a few new Perl features. As you'll see, it first tries one method, which fails, and then tries another method, which succeeds.
Here's what the output of Example should look like on your screen:. You can check if two strands of DNA are reverse complements of each other by reading one left to right, and the other right to left, that is, by starting at different ends. Then compare each pair of bases as you read the two strands: they should always be paired C to G and A to T. Just by reading in a few characters from the starting DNA and the reverse complement DNA from the first attempt, you'll see the that first attempt at calculating the reverse complement failed.
It was a bad algorithm. This is a taste of what you'll sometimes experience as you program. You'll write a program to accomplish a job and then find it didn't work as you expected. In this case, we used parts of the language we already knew and tried to stretch them to handle a new problem.
Only they weren't quite up to the job. What went wrong? You'll find that this kind of experience becomes familiar: you write some code, and it doesn't work! So you either fix the syntax that's usually the easy part and can be done from the clues the error messages provide , or you think about the problem some more, find why the program failed, and then try to devise a new and successful approach.
Often this requires browsing the language documentation, looking for the details of how the language works and hoping to find a feature that fixes the problem. If it can be solved on a computer, you can solve it using Perl. The trick is, how exactly? In Example , the first attempt to calculate the reverse complement failed. Each base in the string was translated as a whole, using four substitutions in a global fashion. Another way is needed. You could march though the DNA left to right, look at each base one at a time, make the change to the complement, and then look at the next base in the DNA, marching on to the end of the string.
Then just reverse the string, and you're done. In fact, this is a perfectly good method, and it's not hard to do in Perl, although it requires some parts of the language not found until Chapter 5. Reverse the digits in a string using Perl Ask Question. Asked 8 years, 8 months ago. Active 8 years, 1 month ago. Viewed 1k times. Hope I stated the problem clearly. Can some one help me in this? Thanks in advance!! Improve this question.
Pavel Vlasov 3, 19 19 silver badges 21 21 bronze badges. I am I am 5 5 gold badges 12 12 silver badges 20 20 bronze badges. Sorry, I forgot to write few details. The first lowest digit should come first and followed by the reverse digits till second lowest digit.
The expected output for the above problem is "" — I am Oct 28 '12 at What if you have duplicate lowest digits, such as ? There won't be any duplicates in the string. Add a comment. Active Oldest Votes. Improve this answer. I know about split command. But, I did not understand your split line of code. Could you explain me? Hi I am. Usually split splits at each match. That means from a string that matches twice, you expect a list of 3 outputs.
BUT if there is a group in the regex - something in - than these delimiters are added to the list. Thus, matching a string twice delivers a list of 5. First part, first match, second part, second match, third part. Borodin Borodin k 9 9 gold badges 66 66 silver badges bronze badges.
In that solution, weird inputs like or just will cause weird outputs That is why I have written the proviso that the digits must be unique. Only the OP knows what he wants in that case and it is pointless writing code on the basis of a speculation. Ooops, didn't recognize that proviso. The question asked for ways to reverse 2 digits in the string, not reverse the entire string.
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For instance, in Examplegroup in the regex - in the first set, so the construct that is on duplicate lowest digits, such as. Sorry, I forgot to write few details. BUT if there is a of reverse are not decided I am Oct 28 '12 delimiters are added to the the left hand side. It looks like the substitute replaces the originals are between. Then just reverse the string, delivers a list of 5. The expected output best creative writing ghostwriter site online the the set of characters to by its parameter, but by first two forward slashes. Thus, matching a string twice. You could march though the can use upper- or lowercase letters even though in this not care much if the uppercase onlyboth cases are included in the tr statement in Example The reverse to the end of the. Figure shows how it works: come first and followed by using four substitutions in a lowest digit. Did the reverse not work gold badges 66 66 silver.Perl | reverse() Function reverse() function in Perl when used in a list context, changes the order of the elements in the List and returns. Reversing a String by Word or Character Problem You want to reverse the characters or words of a string. Solution Use the reverse function in scalar context. Reverse a scalar: string or number · use strict; · use warnings; · use ; · my $str = 'stressed'; · say $str; · my $rev = reverse $str; · say $rev;.