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Converting a String into double?

Posted on 2004-08-10
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Last Modified: 2010-04-24
How is a String converted into double in Visual C++ .NET?
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Question by:judico
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drichards earned 500 total points
ID: 11762596
Is this managed or unmanaged C++?

Managed version:

    System::String *strd = S"123.456";
    double val = System::Double::Parse(strd);


Unmanaged version:

    std::string strd("123.456");        // You could use regular char[] instead
    double val = ::atof(strd.c_str());
   
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Author Comment

by:judico
ID: 11763021
Thanks for the reply. I still cannot do the conversion. The code is managed and I'm declaring these two arrays (having also -- static int ii ;):

static String *LeSTRING[] = new String*[ 1000 ];
static int Le __gc[] = new int __gc[ 1000 ];

and then, in a loop I'm trying the code you posted above, the way I thought it should be applied in this case:

 System::String *strd = LeSTRING[ ii ];
 double Le[ ii ] = System::Double::Parse(strd);

but I get the error messages:

error C2057: expected constant expression
error C2466: cannot allocate an array of constant size 0
error C2440: 'initializing' : cannot convert from 'double' to 'double []'
error C2057: expected constant expression
error C2466: cannot allocate an array of constant size 0
error C2440: 'initializing' : cannot convert from 'double' to 'double []'

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Expert Comment

by:drichards
ID: 11763149
You're trying to declare Le[ii] as a variable of type double, which won't work.  You can just take the implicit conversion from double to int.  Your code should be (assuming you've assigned actual strings into LeSTRING[]):

 System::String *strd = LeSTRING[ ii ];
 Le[ ii ] = System::Double::Parse(strd);
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Author Comment

by:judico
ID: 11763293
Thank you so much for the help. It works very well.

P.S. I increased the points -- let me know if there is any problem.
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LVL 19

Expert Comment

by:drichards
ID: 11763327
You're welcome.  Thanks for the extra points.
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