How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
The compiler does not complain but the actual results when I access
the const double* are incorrect.
Note that the (long double*) is a pointer to an array of long doubles.
16  3812 
"ferran" <fe*****@yahoo. com> wrote in message
news:53******** *************** ***@posting.goo gle.com... How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
Well you've answered your own question.
The compiler does not complain but the actual results when I access
the const double* are incorrect.
Not surprisingly.
Note that the (long double*) is a pointer to an array of long doubles.
I think the question you meant to ask is how to I *convert* an array of long
doubles to an array of doubles, casting is not helpful as you have already
found out.
The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
john
"ferran" <fe*****@yahoo. com> wrote in message
news:53******** *************** ***@posting.goo gle.com... How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
Well you've answered your own question.
The compiler does not complain but the actual results when I access
the const double* are incorrect.
Not surprisingly.
Note that the (long double*) is a pointer to an array of long doubles.
I think the question you meant to ask is how to I *convert* an array of long
doubles to an array of doubles, casting is not helpful as you have already
found out.
The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
john
On Sat, 10 Apr 2004 16:44:44 +0100 in comp.lang.c++, "John Harrison"
<jo************ *@hotmail.com> wrote, The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
Surely there is something better than copying one by one.
std::vector<dou ble> Value1( Value2, Value2+N );
Or at the worst
std::copy(Value 2, Value2+N, Value1);
Why would you ever write a 'for' loop for that? I don't get it.
On Sat, 10 Apr 2004 16:44:44 +0100 in comp.lang.c++, "John Harrison"
<jo************ *@hotmail.com> wrote, The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
Surely there is something better than copying one by one.
std::vector<dou ble> Value1( Value2, Value2+N );
Or at the worst
std::copy(Value 2, Value2+N, Value1);
Why would you ever write a 'for' loop for that? I don't get it.
ferran wrote: How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
The compiler does not complain but the actual results when I access
the const double* are incorrect.
The above cast is only appropriate if you have a long double* that
actually doesn't point to a long double, but to a double.
Note that the (long double*) is a pointer to an array of long doubles.
I guess you actually want to have an array of double. In this case you
have to create a copy of your array.
ferran wrote: How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
The compiler does not complain but the actual results when I access
the const double* are incorrect.
The above cast is only appropriate if you have a long double* that
actually doesn't point to a long double, but to a double.
Note that the (long double*) is a pointer to an array of long doubles.
I guess you actually want to have an array of double. In this case you
have to create a copy of your array.
"David Harmon" <so****@netcom. com> wrote in message
news:40******** *******@news.we st.earthlink.ne t... On Sat, 10 Apr 2004 16:44:44 +0100 in comp.lang.c++, "John Harrison"
<jo************ *@hotmail.com> wrote,The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
Surely there is something better than copying one by one.
std::vector<dou ble> Value1( Value2, Value2+N );
Or at the worst
std::copy(Value 2, Value2+N, Value1);
Why would you ever write a 'for' loop for that? I don't get it.
Granted, but I was just trying to emphasise to the OP that there has to be
some work done to perform the conversion (he was trying to cast), whether
that's done with an explicit loop, or in the internals of std::vector
constructor or std::copy.
john
"David Harmon" <so****@netcom. com> wrote in message
news:40******** *******@news.we st.earthlink.ne t... On Sat, 10 Apr 2004 16:44:44 +0100 in comp.lang.c++, "John Harrison"
<jo************ *@hotmail.com> wrote,The only way to allocate a new array of doubles and copy the long doubles
over to the new array one by one. Something like
double *Value1 = new double[N];
for (int i = 0; i < N; ++i)
Value1[i] = Value2[i];
Surely there is something better than copying one by one.
std::vector<dou ble> Value1( Value2, Value2+N );
Or at the worst
std::copy(Value 2, Value2+N, Value1);
Why would you ever write a 'for' loop for that? I don't get it.
Granted, but I was just trying to emphasise to the OP that there has to be
some work done to perform the conversion (he was trying to cast), whether
that's done with an explicit loop, or in the internals of std::vector
constructor or std::copy.
john
On Sat, 10 Apr 2004 18:24:06 +0100 in comp.lang.c++, "John Harrison"
<jo************ *@hotmail.com> wrote, Granted, but I was just trying to emphasise to the OP that there has to be
some work done to perform the conversion (he was trying to cast), whether
that's done with an explicit loop, or in the internals of std::vector
constructor or std::copy.
Good point; certainly the ultimate conversion from long double to double
must be done one at a time somewhere. Perhaps it could be done without
needing to store the whole set of results. We don't know how the
results are to be used, but perhaps some kind of adapter class might
avoid a copying step. I guess if the destination is hard coded to
require an array of double there is not much choice but to build one. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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How can I cast from (long double*) to (const double*)
I have tried:
const double* Value1 = (const double*)Value2;
The compiler does not complain but the actual results when I access
the const double* are incorrect.
Note that the (long double*) is a pointer to an array of long doubles.
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