Is it possible to make nested structures? I'm trying to do this with the following code, but it just doesn't compile
Code:#include<iostream> using namespace std; struct animals{ struct insects; struct fish; struct mammals; }; struct insects{ char moths[40]; char beatles[40]; char crickets[40]; }; int main(){ animals A; A.insects B; return 0; }
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For one thing, the structs fish and mammals do not exist. The next problem is that you did not provide any names for your member variables. It is as if you wrote:
Code:struct Example { int; char; double; };
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
The code below produces the following compilation error:
My actual purpose in this is to generate a "tree data structure."nestedStruct.cpp:30: error: expected primary-expression before '.' token
nestedStruct.cpp:30: error: expected ';' before "B"
Code:#include<iostream> using namespace std; struct animals{ struct insects; struct fish; struct mammals; }; struct insects{ char moths[40]; char beatles[40]; char crickets[40]; }; struct fish{ char bass[40]; char shark[40]; }; struct mammals{ char gopher[40]; char elephant[40]; }; int main(){ animals A; animals.insects B; return 0; }
What do you mean? It looks as if you want to use inheritance.My actual purpose in this is to generate a "tree data structure."
The closest that I can see to correcting your errors is:
But this is just composition: an Animals object has a Insects object.Code:#include<iostream> using namespace std; struct Insects { char moths[40]; char beatles[40]; char crickets[40]; }; struct Fish { char bass[40]; char shark[40]; }; struct Mammals { char gopher[40]; char elephant[40]; }; struct Animals { Insects insects; Fish fish; Mammals mammals; }; int main() { Animals a; // a.insects is an Insect struct. }
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It looks like animals contains only forward declarations of other classes.Code:struct animals{ struct insects; struct fish; struct mammals; };
You should move it after you have all those structs declared and then declare actual instances of those as members of struct animals.
I might be wrong.
Quoted more than 1000 times (I hope).Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
What I really want to do is dynamically generate a tree structure.
What I can't seem to do in the above code is assign a value to the moths variable.
The way you are doing it means that the tree structure is fixed at compile time. You would need to implement a multiway tree if you actually want a tree structure that can be changed at runtime.What I really want to do is dynamically generate a tree structure.
Of course you can. Just access a.insects.moths.What I can't seem to do in the above code is assign a value to the moths variable.
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