Writing a Word in Reverse

[class_eff]

What is it you are trying to achieve?
The task is basically to enter a word and the program will output the word backwards. (e.g., "backwards" ; output = "sdrawkcab") Also, the program will notify the user if the word is a palindrome (e.g., "madam", "racecar").


What is the problem you are having?
I tried to think of the problem logically, but it didn't work. I think I'm not understanding what the actual task is.

Describe what you have tried to solve this problem
I tried to put the word entered into an array, and swap the positions of each letter in the array so that it appears backwards; however, that didn't work. I have the correct way of doing this program, but I'm not too sure what's actually happening in the code itself.


Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)
This is my attempt. It's somewhat a rough draft so there's probably plenty of errors.

Turing:

var word : string procedure swap2 (x : array 1..* of string) var temp := 0 temp := x(1) x(10) := x(1) x(9) := x(2) x(8) := x(3) x(7) := x(4) x(6) := x(5) x(5) := x(6) x(4) := x(7) x(3) := x(8) x(2) := x(9) x(1) := x(10) x(10) := temp end swap2 for i : 1..length(word) get word : * swap(word) end for

And this is the "correct" way of doing it.

Turing:

var word : string function backwards (x : string) : string var switch : string := ""     for decreasing i : length(x)..1         switch += x(i)     end for result switch end backwards put "Please enter a word." get word put backwards(word) if word = backwards(word) then     put "The word is a palindrome." end if

Any help is greatly appreciated. Thank you in advance!

[Insectoid]

The answer is obvious if you use two strings.

[class_eff]

Meaning?

[Insectoid]

Use one string to input the word, and the other string to store the reversed word. Put the swapped word in the 2nd string one letter at a time. How you do that is for you to figure out.

[Panphobia]

just use two strings and a loop that goes 0 to string.length and then just string2 = string1.charat(loop count) + string2

[class_eff]

Panphobia @ 1/12/2013, 4:50 pm wrote:

just use two strings and a loop that goes 0 to string.length and then just string2 = string1.charat(loop count) + string2

Could you show me an example?

&&, Also, I was wondering if you could explain what's happening in the "correct" code.

[Panphobia]

just make your existing loop into an increasing loop and then just do switch := switch + x(i)

[Insectoid]

Christ, Panphobia. Don't just tell him how to do it. Point him in the right direction. Give hints, maybe. But don't give away the answer.

I guess it doesn't really matter though, since your answers are barely legible and often not even in the right language.

[DemonWasp]

There are a lot of problems with the code you listed:
- only supports strings with length of exactly 10
- Turing doesn't let you assign individual letters in a string, so x(10) := x(1) doesn't work.
- the 'temp' variable is assigned to 0, which makes it an integer, which cannot hold string or character values (without conversion)

The correct version of the code is pretty straightforward:

Turing:

function backwards (x : string) : string     % This variable is poorly named. It will hold the "reversed" string as we build it.     var switch : string := ""     % Go backwards from the end of the given word to its start...     for decreasing i : length(x)..1         % At each letter, add that letter to another string.         switch += x(i)     end for     % Return the reversed string.     result switch end backwards

You should choose a short word, like "dog" and try imagining how the computer will execute the code in the "backwards" function. Use a piece of paper to keep track of the values of variables. If you don't know what something does, look it up in the Turing help (also available online here: http://compsci.ca/holtsoft/doc/)

You should learn how to "read" code like this. Turing is a really easy language to read: it pretty much says what it's doing.

[Panphobia]

Insectoid, I know I should not be giving him the answer yes, but as for the different language stuff, I prefer to call it pseudo code, since concepts are transferable through languages

[Insectoid]

Quote:

I know I should not be giving him the answer

Then why do you keep doing it?

Quote:

I prefer to call it pseudo code

I know what pseudocode is, and what you write is not it. Even it it was passable pseudocode, the algorithms are not easily transferable across languages if OP only knows Turing. OP has no idea what dot notation is. He does not know what changes between languages and what stays the same. We're talking to people who have been programming for a much as a few weeks. Things that are trivial to you are next to impossible for many of the people here.

[class_eff]

DemonWasp @ 1/13/2013, 2:58 pm wrote:

There are a lot of problems with the code you listed:
- only supports strings with length of exactly 10
- Turing doesn't let you assign individual letters in a string, so x(10) := x(1) doesn't work.
- the 'temp' variable is assigned to 0, which makes it an integer, which cannot hold string or character values (without conversion)

The correct version of the code is pretty straightforward:

Turing:

function backwards (x : string) : string     % This variable is poorly named. It will hold the "reversed" string as we build it.     var switch : string := ""     % Go backwards from the end of the given word to its start...     for decreasing i : length(x)..1         % At each letter, add that letter to another string.         switch += x(i)     end for     % Return the reversed string.     result switch end backwards

You should choose a short word, like "dog" and try imagining how the computer will execute the code in the "backwards" function. Use a piece of paper to keep track of the values of variables. If you don't know what something does, look it up in the Turing help (also available online here: http://compsci.ca/holtsoft/doc/)

You should learn how to "read" code like this. Turing is a really easy language to read: it pretty much says what it's doing.

Thanks a lot. I really appreciate the clarification. Seems as though I was just over thinking it.Thanks again!

[Panphobia]

Sorry, I will not give any answers on here anymore.

[Raknarg]

Unless you can reasonably justify doing it, because there are some cases where a user probably won't profit by making him do more work than he has to. Some things are about learning, but some things can just be trivial.