Contest Sign-Up Thread: Rewrite Mid() from VB

Your goal is to rewrite the Mid function found in Visual Basic. You can find information on this function here: http://msdn.microsoft.com/library/de...l/refctMid.asp
Before you go thinking this is a simple task... I assure you it's not. It shouldn't take you too long to code, but it's a real brain buster.

Your Mid() implementation must satisfy the following syntatic forms:
std::string mystring = Mid(someotherstring, 2, 5);
Mid(mystring, 2, 5) = someotherstring;
Mid(mystring, 0, 3) = Mid(someotherstring, 2, 3); // Very tricky

This contest is C++ only (you can't do it in C! (OOPs, there's a hint))The contest will be Run from now until March 7th (that's like 10 days). If you have any questions, or if you'd like to be a judge or a contestant please reply to this thread.

Entries will be sumitted to my email address: [email protected] before 12:00AM (your time) March 7th.

Judges - 3
Eibro
Sang-Drax
golfinguy4
[1 Slot free, please apply]

Contestants - 10
Polymorphic OOP
Travis Dane
*ClownPimp*
MadHatter
Vasanth
Sebastiani
Captain Penguin
jverkoey
Codeplug
DavT

i'm confused... what does it return to make:
Mid(mystring, 2, 5) = someotherstring; //and
Mid(mystring, 0, 3) = Mid(someotherstring, 2, 3); // Very tricky
possible? or is that part of the challange..? ah.. i may do it. don't sign me up yet though...

>This contest is C++ only(you can't do it in C! (OOPs, there's a hint))
i get it.. but.. eh.. sure.. oh well.

i guess i'll be a contestant...

Sounds easy, Count me in.

Quote:

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i'm confused... what does it return to make:
Mid(mystring, 2, 5) = someotherstring; //and
Mid(mystring, 0, 3) = Mid(someotherstring, 2, 3); // Very tricky
possible? or is that part of the challange..?

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Try returning a reference.

-Prelude

Quote:

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Originally posted by Eibro

Mid(mystring, 0, 3) = Mid(someotherstring, 2, 3); // Very tricky

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What exactly is ment with this? Say i pass in some arguments
and the the function returns something and we end up with this

Code:

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 "abc" = "def";

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What is this suppose to mean?

I'm sorry, I can't answer that.

>I'm sorry, I can't answer that.

just a little hint? i'll be yer friend :) ...:rolleyes:

seriously though.. i fail to see how this function would work as an L-value. it seems like it would be like doing something like:

Code:

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std::string x = "abcdefg";
std::string y = "tuvwxyz";
x = Mid(x, 3);  //note the uselessness of this line
x = Mid(y, 3);  //makes the previous line useless

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obviously this isn't how it should be. or maybe it is... bah.. i dunno.

Does this help?

std::string hello = "Hello";
std::string world = "World";

Mid(hello, 0, 2) = Mid(world, 0, 2);
std::cout << hello; // Should print "Wollo";

>Does this help?

very much. thank you. i still don't know how to do it, but atleast now i know what i'm trying to do... ;)

Mid is a simple function to implement in C++. If it's speed that the contest is based on then someone could just use C++ .NET and link that to an MASM function. (cause I doubt inline ASM would work very well with VC6.0)

>Mid is a simple function to implement in C++

to make one such as
std::string mystring = Mid(somestring, 5, 3);
would be easy. but
Mid(somestring, 5, 3) = mystring;
wouldn't be as easy... unless i'm missing something obvious.. which i don't think i am...

What is this being judged on. Speed? Elegance? Efficiency?

Add me in

Quote:

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Originally posted by Polymorphic OOP
What is this being judged on. Speed? Elegance? Efficiency?

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All of the above + Portability + Fidelity
I'll get the exact scheme layed out when I get home.
If you're wondering, you can go look what ygfperson used for the contests he ran... I don't think i'll stray too far from that.

I'm in. :)

Vasanth and Sebastiani added.
I'm sorry, I had to go through and remove posts which gave hints towards the contest. Just so everyone knows where their posts went :)

Do comments count? I don't comment. The code is pretty straight forward. Should I add them in? Will I not get as high is I don't comment?

Meh, if you don't think your code needs them...
If you think I can understand the code without comments then I don't see a reason to.
Some light commenting would be nice though.

is this valid, and if so, what should be printed...

string s1 = "abcdefg";
cout << (Mid(s1, 3, 0) = "123") << endl;

>is this valid, and if so, what should be printed...
string s1 = "abcdefg";
cout << (Mid(s1, 3, 0) = "123") << endl;<

abc123defg

i think

what Mid(string, int, int) = Mid(string, int, int) does, i think, is this...

Code:

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std::string str1 = "abcdefg";
std::String str2 = "tuvwxyv";

Mid(str1, 3, 2) = Mid(str2, 3, 2);
//grab the substring from str1 ("abc[de]fg")
//replace it with the substring from str2 ("abc[wx]fg")
//the end result, held in str1, is "abcwxfg"

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one question... should str2 be altered in this process?

Quote:

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Originally posted by *ClownPimp*
is this valid, and if so, what should be printed...

string s1 = "abcdefg";
cout << (Mid(s1, 3, 0) = "123") << endl;

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Well if you want to implement assignment to const char* then yeah, that's legal.
"abc123defg" would be printed.

Quote:

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one question... should str2 be altered in this process?

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No

Quote:

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Originally posted by Eibro
Well if you want to implement assignment to const char* then yeah, that's legal.
"abc123defg" would be printed.

No

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Hmmm really? I interpretted it as meaning that it would just leave it as abcdefg because the substring was of length 0.

What should happen when you do this?

std::string a = "abc";
Mid( a, 3, 0 ) = "def";

or how about

std::string b = "abc";
Mid( b, 4, 0 ) = "def";

Quote:

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Originally posted by Polymorphic OOP
Hmmm really? I interpretted it as meaning that it would just leave it as abcdefg because the substring was of length 0.

What should happen when you do this?

std::string a = "abc";
Mid( a, 3, 0 ) = "def";

or how about

std::string b = "abc";
Mid( b, 4, 0 ) = "def";

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Hm, yeah, you're right. It's 3AM, what was I thinking?

so... it will only replace, at max, the length given in the first Mid call thingie? i thought it was like..

take substring from left mid, regardless of length, and put in it's place substring from right mid, regardless of length.
so...

Code:

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string str1 = "abc";
string str2 = "123";
Mid(str1, 1, 1) = Mid(str2, 0);

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produces a string holding "a123c"

I am REALLY confused now, ha.

Code:

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string str1 = "abc";
string str2 = "123";
Mid(str1, 1, 1) = Mid(str2, 0);

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take the substring from str1 (starting at index 1, 'b' (index 0 being 'a') and holding 1 character, just the 'b') and replace it with a box

"a[ ]c"

place in that box the substring from str2 (starting at index 0, '1', and holding 3 characters, '123')

"a[123]c"

does that make any sense...? maybe this isn't how it should be done... maybe the "box" should only be able to hold how many characters it held before, meaning it only places the '1' in the "box"... BAH!

The strings should grow and shrink depending on what indicies you pass.
Think of it like this, the lvalue Mid() determines what characters in the lvalue string are replaced. The rvalue Mid() determines what the characters are replaced with in the lvalue Mid().

So YES, I was right the first time.
string s1 = "abcdefg";
cout << (Mid(s1, 3, 0) = "123") << endl;
That should print "abc123defg". Because we're replacing 0 characters at position 3 in s1. If we did something like:
string s1 = "abcdefg";
string s2 = "123";
cout << (Mid(s1, 3, s2.size()) = s2) << endl;
Then "abc123g" would be printed.

count me in... (doesn't mean I'll ever get around to it :) )

Quote:

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Originally posted by Eibro

Judges - 1
Eibro
[2 Slots availible - (I'm not doing this all myself!)]

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I'd like to judge this contest.

Quote:

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Originally posted by Sang-drax
I'd like to judge this contest.

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Finally
Thank you!

Quote:

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Originally posted by Polymorphic OOP
Do comments count?

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Yes, comment the code!

Sure, I'll help out with the judging.

Make sure the code is standard. If it doesn't compile on gcc, I'm gonna be ........ed.

this looks like an interesting one... i remember i already did this one a while back for an Array class i made, i worked in a different manner though, plus i have no $$$$ing clue how it works... so im not gonna be able to relax till i figure it out now, THANKS! THANKS A WHOOLLLLEEE BUNCH!! here goes hours of my life.

edit:: this not an entry.
edit:: its all this one confusing little goddamn line....


edit:: i figured it out... and its genuis, i might add.

might i make this post worht something by wishing all the contestants good luck, and the judges too, hehe.

Quote:

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Originally posted by no-one
this looks like an interesting one... i remember i already did this one a while back for an Array class i made, i worked in a different manner though, plus i have no $$$$ing clue how it works... so im not gonna be able to relax till i figure it out now, THANKS! THANKS A WHOOLLLLEEE BUNCH!! here goes hours of my life.

edit:: this not an entry.
edit:: its all this one confusing little goddamn line....


edit:: i figured it out... and its genuis, i might add.

might i make this post worht something by wishing all the contestants good luck, and the judges too, hehe.

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Cmon, make it an entry!

You can try your functions using this test program.
It tests various syntactic constructions and the resulting strings.

Code:

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int main()
{
    using namespace std;
     
    bool correct = true;
    string s1,s2; 
 
    //Basic test
    s2 = "0123456789";
    string s3 = Mid(s2,1,4);
    s1 = Mid(s2,1,4);
    s2 = Mid("0123456789",1,4);
    if (s1 != "1234" or s2 != "1234" or s3 != "1234")
        cout << "Basic test incorrect : " << s1, correct=false;
   
   
    //First test
    s1 = "abcdefg";
    Mid(s1, 3, 0) = "123";
    if (s1 != "abc123defg")
        cout << "First test incorrect : " << s1, correct=false;
       
       
    //Second test
    s1 = "abcdefg";
    s2 = "123";
    Mid(s1, 3, s2.size()) = s2;
    if (s1 != "abc123g")
        cout << "Second test incorrect : " << s1, correct=false;

    //Third test
    s1 = "abc";
    s2 = "123";
    Mid(s1, 1, 1) = Mid(s2,1);
    if (s1 != "a23c")
        cout << "Third test incorrect : " << s1, correct=false;   
   
    if (correct)
        cout << "All tests correct!";
}

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This may provide some ideas:
Moderator Edit
See VB string functions.


Link removed by Hammer - Too close to giving away answers (bad ones at that), imho.

Some ideas? :) This shows up how to do the whole function, maybe with some changes.

Ahh, and I still think it's possible to do the Mid function with C.

Quote:

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Originally posted by Vber
Some ideas? :) This shows up how to do the whole function, maybe with some changes.

Ahh, and I still think it's possible to do the Mid function with C.

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Okay, prove me wrong by doing it. I certainly can't think of any C constuct which would allow you to have a single "function" act in many different ways.

on the link the guy posted here, there was the "mid" function writen in pure C.

Quote:

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Originally posted by Vber
on the link the guy posted here, there was the "mid" function writen in pure C.

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and it was crap, trust me ;)

Quote:

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Originally posted by Vber
on the link the guy posted here, there was the "mid" function writen in pure C.

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And you could apply "mid(astring,0,2)=mid(astring(2,1);" on it?

i'll be entering, I'll have the code in about 20 mins

Hmmph, 4 hours later and no code?

Hmm maybe I'm just retarded (in fact I'd bet on it!), but the main thing preventing me from writing this code is this:

Mid(s1, 3, 0) = "123";

Apparently my C++ knowledge is too limited, because statements like these don't make much sense to me.

Mid takes a string, the start location, and the end (or 0 for the whole thing?), and returns these characters as a string. At least, that's what it does in the "Basic test". In the "First test" and after, statements like above are rampant - what does it mean?? From my knowledge, it would mean "make a string from s1 starting at the 3rd char going to the end, and then replace that string with "123"" which obviously isn't what happens.

So, what am I missing here? Some C++ concept that I haven't learned or have forgotten?

I'm in.

gg

Added
Need one more judge.

Code:

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Mid(s1, 3, 0) = "123";

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Does this make sense: "Replace 0 characters in s1 at position 3 with '123'"

Quote:

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So, what am I missing here? Some C++ concept that I haven't learned or have forgotten?

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Probably.

here's one possibility with regards to 0 length Mid()'s;

Code:

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string s1 = "abcdefg";
cout << (Mid(s1,3,0) = "123") << endl;

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Output:
abc123defg

gg

lmao, y'know, i posted that earlier, and I got side-tracked on one of my new games....lmao....i guess i probably won't even enter :) sorry bout that

...........thanks for noticing eibro.....lol

Recieved Entries from:
Travis Dane
Codeplug
Sebastiani
Sang-Drax [although he's judging]
Deadline is midnight tommorow.

Contest is over in this timezone! I'll accept any entries I get before I check tommorow.
I've recieved entired from "[email protected]" and "Dorian Boyce", either of you want to enlighten me to your screen name?

What should this code do?

Mid("12345",1,1) = "aaa";

Undefined?
An exception?

I guess the best option would be if it didn't compile at all:

Code:

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const std::string s1 = "abc";
Mid(s1,0) = "123"; //SHOULDN'T COMPILE
Mid("abc",0) = "123" //SHOULDN'T COMPILE

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Dorian Boyce is me

... and [email protected] is me ...

DavT

What's the status here? We still working on some results??

gg

Code:

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const std::string s1 = "abc";
Mid(s1,0) = "123"; //SHOULDN'T COMPILE
Mid("abc",0) = "123" //SHOULDN'T COMPILE

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um yes they should, your forgeting that the assignment works on the returned value or object so, what appears to be an assignment to the function is actually assignement to the functions return.

I agree with you in that it should compile (cuz my version of it does :)). The point that Sang-drax is trying to make is that the first argument to Mid() must be modified in the following cases:

Code:

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string s1 = "abcdef";
Mid(s1, 2, 2) = "123";
if (s1 != "ab123ef") //checking s1, not return value of Mid()
  cout << "incorrect!" << endl;

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So if the first parameter is constant, what do you do? One option is to not let it compile, which in my opinion, limits the functionality unnecessarily.

gg

Quote:

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Originally posted by Codeplug
What's the status here? We still working on some results??

gg

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Waiting for golfinguy4's results.

golfinguy taking his sweet a$$ time....or too busy golfin.

gg

Quote:

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Originally posted by Eibro
Waiting for golfinguy4's results.

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I thought I told you that I never got them and that you should proceed without me.

Quote:

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Originally posted by golfinguy4
I thought I told you that I never got them and that you should proceed without me.

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I posted that long before I ever knew you didn't get the entries.