Invalid use of non-static data member

Question

It's a Heap implemented by myself(for algorithm contest).There are some compilation errors that I can't recover from...

\Map_Heap.cpp|13|error: invalid use of non-static data member 'MapHeap<DT>::nv'| \Map_Heap.cpp|19|error: from this location|

Code:

#include<cstdio> #include<cstring> const int HEAP_SIZE=10005; template<class DT> struct MapHeap { DT f[HEAP_SIZE+5]; int mp1[HEAP_SIZE+5];//val -> index int mp2[HEAP_SIZE+5];//index -> val int nv;///line 13 MapHeap():nv(0) { memset(mp1,-1,sizeof(mp1)); memset(mp2,-1,sizeof(mp2)); } void print(int n=nv)//line 19 { for(int i=1;i<=n;i++) printf("%d ",f[i]); puts(""); for(int i=1;i<=n;i++) printf("%d ",mp1[i]); puts(""); for(int i=1;i<=n;i++) printf("%d ",mp2[i]); puts(""); } };

There are some funny **s at the front. Are these part of the code, or were you trying to make that line bold? Because that won't work in code. — Thomas
– Thomas, Commented Mar 25, 2012 at 19:51
I were just trying to make that line bold and I found it didn't work...>_< — Sayalic
– Sayalic, Commented Mar 25, 2012 at 19:53

Oliver Charlesworth · Accepted Answer · 2012-03-25 19:53:48Z

8

It's simply saying that you can't base a default argument on a member variable. Consider using overloads instead:

void print() { print(nv); } void print(int n) { ... }

answered Mar 25, 2012 at 19:53

Oliver Charlesworth

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3 Comments

Tamer Shlash Over a year ago

Is it mentioned explicitly in the Standards that "you can't base a default argument on a member variable?

Sayalic Over a year ago

wow..It's cool.. It's just steer clear of the problem...(I am not a English native speaker...sorry for my poor English if I make any misunderstanding)

Oliver Charlesworth Over a year ago

@Mr.TAMER. Actually, yes. See 8.3.6, clause 9: "a non-static member shall not be used in a default argument expression".

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