cpp/cs104/classes/ctor-init-list-shadow Source

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Description
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shown to student

Figure out why <tt>m1</tt> and <tt>m2</tt> do not have the expected values of <tt>3.8</tt> and <tt>3.95</tt>, respectively.

</ol>
Learning goal: 
<ul><li>Beware of declaring variables that shadow a member</li>
<li>Use the constructor initialization list to initialize members</li>
</ul>
Epilogue
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shown when solved

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Remarks
Comments, history, license, etc.

Copied from problem cpp/cs104/classes/ctor-initialization-list (author: redekopp@usc.edu)
Copied from problem cpp/cs104/classes/ctor-dtor-members (author: redekopp@usc.edu)
Copied from problem cpp/cs104/classes/ctor-default (author: redekopp@usc.edu)
Copied from problem cpp/cs104/classes/constructor_init (author: redekopp@usc.edu)

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Engine
Choices
json list of string, bool pairs
e.g. [["good", true], ["bad", false]]

Correct answer
Template / Reference solution

Template / Reference solution

#include <iostream>
#include <algorithm>
using namespace std;

struct A1 {
\[
REDACTED
\show:
A1() { x = 1.0; cout << "Default A1 ctor - x = " << x << endl; }
A1(double myx) { x = myx; cout << "Init A1 ctor - x = " << x << endl; }
~A1() { cout << "A1 dtor - x = " << x << endl; }
double x;
]\
};

class A2 {
public:
\[
REDACTED
\show:
A2() { A1 m1(3.8); A1 m2(3.95); cout << "Default A2 ctor" << endl;}
~A2() { cout << "A2 dtor" << endl; }
]\
void print() const { cout << "m1=" << m1.x << " m2=" << m2.x << endl;}
private:
A1 m1;
A1 m2;
};
int main()
{
\[
REDACTED
\show:
A2 obj1;
obj1.print();
]\
return 0;
}

Java test suite
See manual

C++ test suite
json list of stdin/args tests
e.g. [{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]
to just run once with no input use [{}]

[{}]
C++ test suite
See manual

Forbidden substrings
json list of strings
e.g. ["for","while"]

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Solution visibility remove
Java imports
json list of importables
e.g. ["java.util.*"]

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Override Java classname
else defaults to
websheet name
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Dependent on other websheets?
json list of websheet names in this folder
e.g. ["DataStructure"]

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Is example?
i.e., just a demo
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Add compiler flag(s)
json list of flags
e.g. ["-Wno-unused-variable"]

["-w"]
remove
Remove default compiler flag(s)
json list of flags
see default_cppflags
e.g. ["-Wno-write-strings"]

remove

Property	Value
Description html markup shown to student	Figure out why <tt>m1</tt> and <tt>m2</tt> do not have the expected values of <tt>3.8</tt> and <tt>3.95</tt>, respectively. </ol> <p><strong>Learning goal:</strong> </p> <ul><li>Beware of <strong>declaring variables that shadow a member</strong></li> <li>Use the constructor initialization list to initialize members</li> </ul>
Epilogue html markup shown when solved	remove
Public permissions	remove
Remarks Comments, history, license, etc.	Copied from problem cpp/cs104/classes/ctor-initialization-list (author: redekopp@usc.edu) Copied from problem cpp/cs104/classes/ctor-dtor-members (author: redekopp@usc.edu) Copied from problem cpp/cs104/classes/ctor-default (author: redekopp@usc.edu) Copied from problem cpp/cs104/classes/constructor_init (author: redekopp@usc.edu) remove
Engine
Choices json list of string, bool pairs e.g. `[["good", true], ["bad", false]]`
Correct answer
Template / Reference solution
Template / Reference solution	#include <iostream> #include <algorithm> using namespace std; struct A1 { \[ REDACTED \show: A1() { x = 1.0; cout << "Default A1 ctor - x = " << x << endl; } A1(double myx) { x = myx; cout << "Init A1 ctor - x = " << x << endl; } ~A1() { cout << "A1 dtor - x = " << x << endl; } double x; ]\ }; class A2 { public: \[ REDACTED \show: A2() { A1 m1(3.8); A1 m2(3.95); cout << "Default A2 ctor" << endl;} ~A2() { cout << "A2 dtor" << endl; } ]\ void print() const { cout << "m1=" << m1.x << " m2=" << m2.x << endl;} private: A1 m1; A1 m2; }; int main() { \[ REDACTED \show: A2 obj1; obj1.print(); ]\ return 0; }
Java test suite See manual
C++ test suite json list of stdin/args tests e.g. `[{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]` to just run once with no input use `[{}]`	[{}]
C++ test suite See manual
Forbidden substrings json list of strings e.g. `["for","while"]`	remove
Solution visibility	remove
Java imports json list of importables e.g. `["java.util.*"]`	remove
Override Java classname else defaults to websheet name	remove
Dependent on other websheets? json list of websheet names in this folder e.g. `["DataStructure"]`	remove
Is example? i.e., just a demo	remove
Add compiler flag(s) json list of flags e.g. `["-Wno-unused-variable"]`	["-w"] remove
Remove default compiler flag(s) json list of flags see default_cppflags e.g. `["-Wno-write-strings"]`	remove

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