Problem 44313. "Cody" * 5 == "CodyCodyCodyCodyCody"

Created by Peng Liu

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Alice: What? "Cody" * 5 == "CodyCodyCodyCodyCody"? You've gotta be kidding me!Bob: No, I am serious! Python supports such "multiplication" of strings, which actually means replication of strings!Alice: Really?Bob: Modern languages (C++, Java, Python, etc) tend to use native operators (via overloading) to perform simple string manipulations, such as + for string concatenation (e.g., "Cody" + "Cody" == "CodyCody"). Also, Python adopts * to perform string replication. Since R2016b, MATLAB has followed the same convention by introducing the + operator to perform string concatenation (See <a href = "https://www.mathworks.com/matlabcentral/cody/problems/43663-combine-the-first-and-last-names">Problem 43663</a> for a Cody example). Nevertheless, as of R2017b, there is no support for the * operator (or any other operators) which performs string replication in MATLAB.Alice: Sounds like there is a gap...Bob: You got it. Now, I'd like you to fill the gap by using whatever method (preferably overloading) to make * perform string replication in Cody (similar to * in Python), e.g.,<pre class="language-matlab">&gt;&gt; "Cody" * 2
ans = 
 "CodyCody"
</pre><pre class="language-matlab">&gt;&gt; 3 * "Cody"
 ans = 
 "CodyCodyCody"
</pre>Alice: Gotcha. Let me give it a try.

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2032 Solutions
366 Solvers

Last Solution submitted on Aug 05, 2020

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7 Comments

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Andrew Newell on 1 Dec 2017

It's a little scary redefining mtimes this way! As soon as I solved it, I deleted the function.

Rafael S.T. Vieira on 4 Jul 2020

Cody is not allowing overloading the built-in function mtimes.

Nikolaos Nikolaou on 11 Jul 2020 at 13:10

am confused is overloading possible here or not?

Rafael S.T. Vieira on 26 Jul 2020 at 1:12

It is not. I solved overwriting the function assessFunctionAbsence, which is not the goal of the problem. Within this function, I created a file that contained my solution f = fopen("mtimes.m", "w").

Rafael S.T. Vieira on 26 Jul 2020 at 1:23

There are other problems in Cody with this same issue, but without a non-builtin function to overwrite. I've notified their creators and the Cody team, but sadly nothing was done so far. It's the weirdest thing since MATLAB does allow me to do it with a big warning nonetheless.

Rafael S.T. Vieira on 26 Jul 2020 at 1:34

Imho, Authors should have a chance to update their problems, but if they don't, these problems should be deleted. Unless a problem deals with object-oriented programming, requiring overwriting is not promoting good programming practices. That's why MATLAB complains if we do it without classes.

Rafael S.T. Vieira on 26 Jul 2020 at 15:17

To solve a lot of issues within Cody, a set of X different problems could run the reference solutions once by week or by month. If the reference solutions don't work, then authors are notified to update their problems within some fixed time period. There is no point to keep storing problems that are unsolvable and may be used by some authors for unsportive activities (which is not the case here). Deleted problems could even subtract points from everyone that solved them.

PS: Notice that this could even prevent people from posting their homework as a problem for people to solve when a working reference solution is obliged.

Solution Comments

Solution 2693783

1 Comment

1 Comment

hagege ruben on 14 Jul 2020 at 18:42

it seems like there is a bug here: how am I supposed to overload mtimes without using it? (assert failed here on all test saying: The function mtimes is a built-in MATLAB function. Please use a different function name.
)

Solution 2227660

1 Comment

1 Comment

Wayne on 21 Apr 2020

I'm kind of hung up. function y=mtimes(a,b) works just fine on my computer running 2018a. However when used here, Cody gripes at me about using a different function name since mtimes is built in and fails me. Changing the name to something else (asdf, for instance) fails since I haven't modified mtimes to handle strings. What am I missing?

Solution 2173746

3 Comments

3 Comments

Binbin Qi on 25 Mar 2020

cheat!?

Asif Newaz on 26 Mar 2020

I thought this problem is no longer solvable since mtimes is a built-in function. There might be a way that I don't know of

Binbin Qi on 26 Mar 2020

@Asif, I see, sorry

Solution 1292282

1 Comment

1 Comment

T. Dunker on 17 Oct 2017

Actually, this is not a correct solution. The else branch leads to infinite recursion.

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Problem 44313. "Cody" * 5 == "CodyCodyCodyCodyCody"

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Problem 44313. "Cody" * 5 == "CodyCodyCodyCodyCody"

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