«

Hi

using lower_bound I want to pass a 2-dimensional array eg like this:
static const int tbl[5][3] = {
1000, 800, 801,
1001, 802, 803,
1002, 804, 805,
1003, 806, 807,
1004, 808, 809
};

I want to search in only the first column - eg the numbers 1000-1004.
I am trying to find the position in this 2-dimensional array, and then
once located I can access elements[position][1] and elements[position]
[2].

I tried this:
int arrsize = sizeof(tbl)/sizeof(tbl[0]);
low=lower_bound(tbl[0], tbl[0]+arrsize, 7);

But get compile error C2440 cannot convert from 'const int *' to 'int
*'

How can I do this?

Angus

On 3/7/2011 12:17 PM, Angus wrote:
> using lower_bound I want to pass a 2-dimensional array eg like this:
> static const int tbl[5][3] = {
> 1000, 800, 801,
> 1001, 802, 803,
> 1002, 804, 805,
> 1003, 806, 807,
> 1004, 808, 809
> };
>
> I want to search in only the first column - eg the numbers 1000-1004.
> I am trying to find the position in this 2-dimensional array, and then
> once located I can access elements[position][1] and elements[position]
> [2].
>
> I tried this:
> int arrsize = sizeof(tbl)/sizeof(tbl[0]);
> low=lower_bound(tbl[0], tbl[0]+arrsize, 7);
>
> But get compile error C2440 cannot convert from 'const int *' to 'int
> *'
>
> How can I do this?

You should probably provide your own iterator, which when incremented
will skip the rest of the "row".

V
--
I do not respond to top-posted replies, please don't ask

On Mar 7, 6:05*pm, Victor Bazarov <v.baza...@comcast.invalid> wrote:
> On 3/7/2011 12:17 PM, Angus wrote:
>
>
>
>
>
>
>
>
>
> > using lower_bound I want to pass a 2-dimensional array eg like this:
> > * * static const int tbl[5][3] = {
> > * * * *1000, 800, 801,
> > * * * *1001, 802, 803,
> > * * * *1002, 804, 805,
> > * * * *1003, 806, 807,
> > * * * *1004, 808, 809
> > * * };
>
> > I want to search in only the first column - eg the numbers 1000-1004.
> > I am trying to find the position in this 2-dimensional array, and then
> > once located I can access elements[position][1] and elements[position]
> > [2].
>
> > I tried this:
> > * * int arrsize = sizeof(tbl)/sizeof(tbl[0]);
> > * * low=lower_bound(tbl[0], tbl[0]+arrsize, 7);
>
> > But get compile error C2440 cannot convert from 'const int *' to 'int
> > *'
>
> > How can I do this?
>
> You should probably provide your own iterator, which when incremented
> will skip the rest of the "row".
>
> V
> --
> I do not respond to top-posted replies, please don't ask

Are you suggesting it 'jump' over the other items in row. Eg if there
were five columns of ints it would jump 5 int's worth on each
iteration?

Can you provide an outline example? Or place to find something like
this?

On 3/7/2011 1:16 PM, Angus wrote:
> On Mar 7, 6:05 pm, Victor Bazarov<v.baza...@comcast.invalid> wrote:
>> On 3/7/2011 12:17 PM, Angus wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>> using lower_bound I want to pass a 2-dimensional array eg like this:
>>> static const int tbl[5][3] = {
>>> 1000, 800, 801,
>>> 1001, 802, 803,
>>> 1002, 804, 805,
>>> 1003, 806, 807,
>>> 1004, 808, 809
>>> };
>>
>>> I want to search in only the first column - eg the numbers 1000-1004.
>>> I am trying to find the position in this 2-dimensional array, and then
>>> once located I can access elements[position][1] and elements[position]
>>> [2].
>>
>>> I tried this:
>>> int arrsize = sizeof(tbl)/sizeof(tbl[0]);
>>> low=lower_bound(tbl[0], tbl[0]+arrsize, 7);
>>
>>> But get compile error C2440 cannot convert from 'const int *' to 'int
>>> *'
>>
>>> How can I do this?
>>
>> You should probably provide your own iterator, which when incremented
>> will skip the rest of the "row".
>>
>> V
>> --
>> I do not respond to top-posted replies, please don't ask
>
> Are you suggesting it 'jump' over the other items in row. Eg if there
> were five columns of ints it would jump 5 int's worth on each
> iteration?

Yes, that's exactly what I'm suggesting.

> Can you provide an outline example? Or place to find something like
> this?

Something like this:

template<class T, size_type N, size_type M>
class arr_col_iter_t
{
T (&arr)[N][M];
size_type col;
size_type ind;
public:
arr_col_iter_t(T (&a)[N][M], size_type c, size_type ind0)
: arr(a), col(c), ind(ind0) {}

T& operator *() { return arr[ind][col]; }
arr_col_iter_t& operator++() { ++ind; return *this; }
arr_col_iter_t operator++(int) {
arr_col_iter_t temp(*this);
++ind; return temp;
}

bool operator!=(arr_col_iter_t const& other) const
{
assert(&arr == &other.arr
&& col == other.col); // same array, same col
return ind != other.ind;
}
};

template<class T, size_type N, size_type M>
arr_col_iter_t<T,N,M> arr_iter(T (&arr)[N][M], size_type c,
size_type ind0 = 0)
{
return arr_col_iter_t<T,N,M>(arr, c, ind0);
}
...
// to iterate over "column 0" from 0 to arrsize-1:
lower_boundary(arr_iter(tbl, 0), arr_iter(tb, 0, arrsize), 7);

There are undoubtedly holes in that (not to mention that it's not a
fully fledged iterator according to Standard's requirements - no tag, no
value_type, etc.)

V
--
I do not respond to top-posted replies, please don't ask

On Mar 7, 6:05 pm, Victor Bazarov <v.baza...@comcast.invalid> wrote:
> On 3/7/2011 12:17 PM, Angus wrote:
> > using lower_bound I want to pass a 2-dimensional array eg like this:
> > static const int tbl[5][3] = {
> > 1000, 800, 801,
> > 1001, 802, 803,
> > 1002, 804, 805,
> > 1003, 806, 807,
> > 1004, 808, 809
> > };

> > I want to search in only the first column - eg the numbers 1000-1004.
> > I am trying to find the position in this 2-dimensional array, and then
> > once located I can access elements[position][1] and elements[position]
> > [2].

> > I tried this:
> > int arrsize = sizeof(tbl)/sizeof(tbl[0]);
> > low=lower_bound(tbl[0], tbl[0]+arrsize, 7);

> > But get compile error C2440 cannot convert from 'const int *' to 'int
> > *'

That's because you're passing tbl[0], instead of just tbl.

Of course, if you pass tbl, tbl+arrsize, you'll still get an
error when lower_bound trys to do int[3] < 7. Or something like
that: C style arrays are pretty broken, and you can get some
strange effects from them. I recently had to do something
similar, but with several different arrays with different
numbers of rows. The template function to handle this was
something like:

template <size_t N, size_t M>
std::string const (&
findIt(std::string const(&target)[N][M],
int id_column,
std::string const& key)
)[M]
{
// ...
}

(From memory, so it might not be exact.)

Anyway, what you need to do is pass tbl and tbl + arrsize (type
int (*)[3]), and provide a less than operator along the lines of

struct LessThanFirstOfThree
{
bool operator()(int (&arr)[3], int other) const
{
return arr[0] < other;
}
bool operator()(int other, int (&arr)[3]) const
{
return other < arr[0];
}
};

(That's without trying it, so there are likely some typos or
other errors, but that's the general idea.)

> > How can I do this?

> You should probably provide your own iterator, which when incremented
> will skip the rest of the "row".

I'm not sure that that's the solution. He has an array of [] of
[3] int; an iterator into it will designate and array of [3]
int. Doing this with C style arrays and pointers can lead to
some very unnatural syntax, but is doable. Typedef's can help a
lot. (In my example above, I couldn't use a typedef because it
was a template, but my earlier versions, before it became a
template, used typedef's, and weren't that bad.) Something
like:

typedef int Row[3];
Row const array[] = { ... };

Row const& element = std::lower_bound( begin( array ),
end( array ),
int key,
CompareFirst() );

(with CompareFirst something like the above.)

--
James Kanze

On Mar 7, 10:32*pm, James Kanze <james.ka...@gmail.com> wrote:
> On Mar 7, 6:05 pm, Victor Bazarov <v.baza...@comcast.invalid> wrote:
>
>
>
>
>
>
>
>
>
> > On 3/7/2011 12:17 PM, Angus wrote:
> > > using lower_bound I want to pass a 2-dimensional array eg like this:
> > > * * static const int tbl[5][3] = {
> > > * * * *1000, 800, 801,
> > > * * * *1001, 802, 803,
> > > * * * *1002, 804, 805,
> > > * * * *1003, 806, 807,
> > > * * * *1004, 808, 809
> > > * * };
> > > I want to search in only the first column - eg the numbers 1000-1004.
> > > I am trying to find the position in this 2-dimensional array, and then
> > > once located I can access elements[position][1] and elements[position]
> > > [2].
> > > I tried this:
> > > * * int arrsize = sizeof(tbl)/sizeof(tbl[0]);
> > > * * low=lower_bound(tbl[0], tbl[0]+arrsize, 7);
> > > But get compile error C2440 cannot convert from 'const int *' to 'int
> > > *'
>
> That's because you're passing tbl[0], instead of just tbl.
>
> Of course, if you pass tbl, tbl+arrsize, you'll still get an
> error when lower_bound trys to do int[3] < 7. *Or something like
> that: C style arrays are pretty broken, and you can get some
> strange effects from them. *I recently had to do something
> similar, but with several different arrays with different
> numbers of rows. *The template function to handle this was
> something like:
>
> * * template <size_t N, size_t M>
> * * std::string const (&
> * * * * * * findIt(std::string const(&target)[N][M],
> * * * * * * * * * *int id_column,
> * * * * * * * * * *std::string const& key)
> * * * * )[M]
> * * {
> * * * * // *...
> * * }
>
> (From memory, so it might not be exact.)
>
> Anyway, what you need to do is pass tbl and tbl + arrsize (type
> int (*)[3]), and provide a less than operator along the lines of
>
> * * struct LessThanFirstOfThree
> * * {
> * * * * bool operator()(int (&arr)[3], int other) const
> * * * * {
> * * * * * * return arr[0] < other;
> * * * * }
> * * * * bool operator()(int other, int (&arr)[3]) const
> * * * * {
> * * * * * * return other < arr[0];
> * * * * }
> * * };
>
> (That's without trying it, so there are likely some typos or
> other errors, but that's the general idea.)
>
> > > How can I do this?
> > You should probably provide your own iterator, which when incremented
> > will skip the rest of the "row".
>
> I'm not sure that that's the solution. *He has an array of [] of
> [3] int; an iterator into it will designate and array of [3]
> int. *Doing this with C style arrays and pointers can lead to
> some very unnatural syntax, but is doable. *Typedef's can help a
> lot. *(In my example above, I couldn't use a typedef because it
> was a template, but my earlier versions, before it became a
> template, used typedef's, and weren't that bad.) *Something
> like:
>
> * * typedef int Row[3];
> * * Row const array[] = { ... };
>
> * * Row const& element = std::lower_bound( begin( array ),
> * * * * * * * * * * * * * * * * * * * * * *end( array ),
> * * * * * * * * * * * * * * * * * * * * * *int key,
> * * * * * * * * * * * * * * * * * * * * * *CompareFirst() );
>
> (with CompareFirst something like the above.)
>
> --
> James Kanze

Hello

I am trying to progress with code as simple as possible as a learning
exercise.

Here is my code which finds if code in column 1, but not if number
searched is less than any item in first column.

What am I doing wrong?

Here is code:

#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>

using namespace std;

struct errorinfo
{
errorinfo() : category(0), error(0) {}
int category;
int error;
};

bool lessthanrow1(const int (&arr)[3], const int other)
{
return arr[0] < other;
}


bool mapBW2CSTAError(const int bw_error, errorinfo& csta_error)
{
const int cols = 3;
//in real life much bigger array.
static const int tbl[6][cols] = {
1000, 10, 0,
1001, 11, 1,
1200, 12, 2,
4002, 13, 3,
8090, 14, 4,
121105, 15, 5
};

int tblsize = sizeof(tbl) /( sizeof(int) * cols);

int* result = (int*)lower_bound(tbl, tbl+tblsize, bw_error,
lessthanrow1);
int idx = ((result - (int*)tbl) / cols);

if(idx != tblsize){
csta_error.category = tbl[idx][1];
csta_error.error = tbl[idx][2];
} else {
cout << "item not found\n";
return false;
}

cout << "Your error: " << bw_error << " category=" << tbl[idx][1]
<< " errcode=" << tbl[idx][2] << endl;

return true;
}

int main(){
//4002 found ok. 90 returns first element in array. large number
is ok.

errorinfo err;
if(mapBW2CSTAError(4002, err))
cout << "error code used for lookup: " << 4002 << ", type: " <<
err.category << ", specific error code: " << err.error << endl;
else
cout << "error 4002 not recognised\n";


if(mapBW2CSTAError(90, err))
cout << "error code used for lookup: " << 90 << ", type: " <<
err.category << ", specific error code: " << err.error << endl;
else
cout << "error 90 not recognised\n";

if(mapBW2CSTAError(999999, err))
cout << "error code used for lookup: " << 999999 << ", type: "
<< err.category << ", specific error code: " << err.error << endl;
else
cout << "error 999999 not recognised\n";


return 0;
}

On Mar 7, 10:32*pm, James Kanze <james.ka...@gmail.com> wrote:
> On Mar 7, 6:05 pm, Victor Bazarov <v.baza...@comcast.invalid> wrote:
>
>
>
>
>
>
>
>
>
> > On 3/7/2011 12:17 PM, Angus wrote:
> > > using lower_bound I want to pass a 2-dimensional array eg like this:
> > > * * static const int tbl[5][3] = {
> > > * * * *1000, 800, 801,
> > > * * * *1001, 802, 803,
> > > * * * *1002, 804, 805,
> > > * * * *1003, 806, 807,
> > > * * * *1004, 808, 809
> > > * * };
> > > I want to search in only the first column - eg the numbers 1000-1004.
> > > I am trying to find the position in this 2-dimensional array, and then
> > > once located I can access elements[position][1] and elements[position]
> > > [2].
> > > I tried this:
> > > * * int arrsize = sizeof(tbl)/sizeof(tbl[0]);
> > > * * low=lower_bound(tbl[0], tbl[0]+arrsize, 7);
> > > But get compile error C2440 cannot convert from 'const int *' to 'int
> > > *'
>
> That's because you're passing tbl[0], instead of just tbl.
>
> Of course, if you pass tbl, tbl+arrsize, you'll still get an
> error when lower_bound trys to do int[3] < 7. *Or something like
> that: C style arrays are pretty broken, and you can get some
> strange effects from them. *I recently had to do something
> similar, but with several different arrays with different
> numbers of rows. *The template function to handle this was
> something like:
>
> * * template <size_t N, size_t M>
> * * std::string const (&
> * * * * * * findIt(std::string const(&target)[N][M],
> * * * * * * * * * *int id_column,
> * * * * * * * * * *std::string const& key)
> * * * * )[M]
> * * {
> * * * * // *...
> * * }
>
> (From memory, so it might not be exact.)
>
> Anyway, what you need to do is pass tbl and tbl + arrsize (type
> int (*)[3]), and provide a less than operator along the lines of
>
> * * struct LessThanFirstOfThree
> * * {
> * * * * bool operator()(int (&arr)[3], int other) const
> * * * * {
> * * * * * * return arr[0] < other;
> * * * * }
> * * * * bool operator()(int other, int (&arr)[3]) const
> * * * * {
> * * * * * * return other < arr[0];
> * * * * }
> * * };
>
> (That's without trying it, so there are likely some typos or
> other errors, but that's the general idea.)
>
> > > How can I do this?
> > You should probably provide your own iterator, which when incremented
> > will skip the rest of the "row".
>
> I'm not sure that that's the solution. *He has an array of [] of
> [3] int; an iterator into it will designate and array of [3]
> int. *Doing this with C style arrays and pointers can lead to
> some very unnatural syntax, but is doable. *Typedef's can help a
> lot. *(In my example above, I couldn't use a typedef because it
> was a template, but my earlier versions, before it became a
> template, used typedef's, and weren't that bad.) *Something
> like:
>
> * * typedef int Row[3];
> * * Row const array[] = { ... };
>
> * * Row const& element = std::lower_bound( begin( array ),
> * * * * * * * * * * * * * * * * * * * * * *end( array ),
> * * * * * * * * * * * * * * * * * * * * * *int key,
> * * * * * * * * * * * * * * * * * * * * * *CompareFirst() );
>
> (with CompareFirst something like the above.)
>
> --
> James Kanze

I have had a go as below. But there is a problem if lookup value is
smaller than any code in first column. What am I doing wrong? I
assume my predicate is not quite correct?


#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>

using namespace std;

struct errorinfo
{
errorinfo() : category(0), error(0) {}
int category;
int error;
};

bool lessthanrow1(const int (&arr)[3], const int other)
{
return arr[0] < other;
}


bool maperror2code(const int bw_error, errorinfo& csta_error)
{
const int cols = 3;
//in real life much bigger array.
static const int tbl[6][cols] = {
1000, 10, 0,
1001, 11, 1,
1200, 12, 2,
4002, 13, 3,
8090, 14, 4,
121105, 15, 5
};

int tblsize = sizeof(tbl) /( sizeof(int) * cols);

int* result = (int*)lower_bound(tbl, tbl+tblsize, bw_error,
lessthanrow1);
int idx = ((result - (int*)tbl) / cols);

if(idx != tblsize){
csta_error.category = tbl[idx][1];
csta_error.error = tbl[idx][2];
} else {
cout << "item not found\n";
return false;
}

cout << "Your error: " << bw_error << " category=" << tbl[idx][1]
<< " errcode=" << tbl[idx][2] << endl;

return true;
}

int main(){
//4002 found ok. 90 returns first element in array. large number
is ok.

errorinfo err;
if(maperror2code(4002, err))
cout << "error code used for lookup: " << 4002 << ", type: " <<
err.category << ", specific error code: " << err.error << endl;
else
cout << "error 4002 not recognised\n";


if(maperror2code(90, err))
cout << "error code used for lookup: " << 90 << ", type: " <<
err.category << ", specific error code: " << err.error << endl;
else
cout << "error 90 not recognised\n";

if(maperror2code(999999, err))
cout << "error code used for lookup: " << 999999 << ", type: "
<< err.category << ", specific error code: " << err.error << endl;
else
cout << "error 999999 not recognised\n";


return 0;
}

On 3/9/2011 8:48 AM, Angus wrote:
> I have had a go as below. But there is a problem if lookup value is
> smaller than any code in first column. What am I doing wrong? I
> assume my predicate is not quite correct?
>
>
> #pragma warning(disable: 4786)
>
> #include<iostream>
> #include<algorithm>
>
> using namespace std;
>
> struct errorinfo
> {
> errorinfo() : category(0), error(0) {}
> int category;
> int error;
> };
>
> bool lessthanrow1(const int (&arr)[3], const int other)
> {
> return arr[0]< other;
> }
>
>
> bool maperror2code(const int bw_error, errorinfo& csta_error)
> {
> const int cols = 3;
> //in real life much bigger array.
> static const int tbl[6][cols] = {
> 1000, 10, 0,
> 1001, 11, 1,
> 1200, 12, 2,
> 4002, 13, 3,
> 8090, 14, 4,
> 121105, 15, 5
> };
>
> int tblsize = sizeof(tbl) /( sizeof(int) * cols);
>
> int* result = (int*)lower_bound(tbl, tbl+tblsize, bw_error,
> lessthanrow1);

Microsoft C++ 2008 and Comeau C++ (online) refuse to compile the line
above. How did you manage to run your program (if you did)? What
compiler allows you to use 'tbl' and 'tbl+tblsize' for the first and the
second arguments of 'lower_bound'?

> int idx = ((result - (int*)tbl) / cols);
>
> if(idx != tblsize){
> csta_error.category = tbl[idx][1];
> csta_error.error = tbl[idx][2];
> } else {
> cout<< "item not found\n";
> return false;
> }
>
> cout<< "Your error: "<< bw_error<< " category="<< tbl[idx][1]
> << " errcode="<< tbl[idx][2]<< endl;
>
> return true;
> }
>
> int main(){
> //4002 found ok. 90 returns first element in array. large number
> is ok.
>
> errorinfo err;
> if(maperror2code(4002, err))
> cout<< "error code used for lookup: "<< 4002<< ", type: "<<
> err.category<< ", specific error code: "<< err.error<< endl;
> else
> cout<< "error 4002 not recognised\n";
>
>
> if(maperror2code(90, err))
> cout<< "error code used for lookup: "<< 90<< ", type: "<<
> err.category<< ", specific error code: "<< err.error<< endl;
> else
> cout<< "error 90 not recognised\n";
>
> if(maperror2code(999999, err))
> cout<< "error code used for lookup: "<< 999999<< ", type:"
> << err.category<< ", specific error code: "<< err.error<< endl;
> else
> cout<< "error 999999 not recognised\n";
>
>
> return 0;
> }

V
--
I do not respond to top-posted replies, please don't ask

On Mar 9, 2:28*pm, Victor Bazarov <v.baza...@comcast.invalid> wrote:
> On 3/9/2011 8:48 AM, Angus wrote:
>
>
>
>
>
>
>
>
>
> > I have had a go as below. *But there is a problem if lookup value is
> > smaller than any code in first column. *What am I doing wrong? *I
> > assume my predicate is not quite correct?
>
> > #pragma warning(disable: 4786)
>
> > #include<iostream>
> > #include<algorithm>
>
> > using namespace std;
>
> > struct errorinfo
> > {
> > * * errorinfo() : category(0), error(0) {}
> > * * int category;
> > * * int error;
> > };
>
> > bool lessthanrow1(const int (&arr)[3], const int other)
> > {
> > * * return arr[0]< *other;
> > }
>
> > bool maperror2code(const int bw_error, errorinfo& *csta_error)
> > {
> > * * const int cols = 3;
> > * * //in real life much bigger array.
> > * * static const int tbl[6][cols] = {
> > * * * *1000, 10, 0,
> > * * * *1001, 11, 1,
> > * * * *1200, 12, 2,
> > * * * *4002, 13, 3,
> > * * * *8090, 14, 4,
> > * * *121105, 15, 5
> > * * };
>
> > * * int tblsize = sizeof(tbl) /( sizeof(int) * cols);
>
> > * * int* result = (int*)lower_bound(tbl, tbl+tblsize, bw_error,
> > lessthanrow1);
>
> Microsoft C++ 2008 and Comeau C++ (online) refuse to compile the line
> above. *How did you manage to run your program (if you did)? *What
> compiler allows you to use 'tbl' and 'tbl+tblsize' for the first and the
> second arguments of 'lower_bound'?
>
>
>
>
>
>
>
>
>
> > * * int idx = ((result - (int*)tbl) / cols);
>
> > * * if(idx != tblsize){
> > * * * *csta_error.category = tbl[idx][1];
> > * * * *csta_error.error = tbl[idx][2];
> > * * } else {
> > * * * *cout<< *"item not found\n";
> > * * * *return false;
> > * * }
>
> > * * cout<< *"Your error: "<< *bw_error<< *" category="<< *tbl[idx][1]
> > << *" errcode="<< *tbl[idx][2]<< *endl;
>
> > * * return true;
> > }
>
> > int main(){
> > * * //4002 found ok. *90 returns first element in array. *largenumber
> > is ok.
>
> > * * errorinfo err;
> > * * if(maperror2code(4002, err))
> > * * * *cout<< *"error code used for lookup: "<< *4002<< *", type: "<<
> > err.category<< *", specific error code: "<< *err.error<< *endl;
> > * * else
> > * * * *cout<< *"error 4002 not recognised\n";
>
> > * * if(maperror2code(90, err))
> > * * * *cout<< *"error code used for lookup: "<< *90<< *",type: "<<
> > err.category<< *", specific error code: "<< *err.error<< *endl;
> > * * else
> > * * * *cout<< *"error 90 not recognised\n";
>
> > * * if(maperror2code(999999, err))
> > * * * *cout<< *"error code used for lookup: "<< *999999<< *", type:"
> > << *err.category<< *", specific error code: "<< *err.error<< *endl;
> > * * else
> > * * * *cout<< *"error 999999 not recognised\n";
>
> > * * return 0;
> > }
>
> V
> --
> I do not respond to top-posted replies, please don't ask

That works on VC++ v6. Otherwise can use lower_bound(&tbl[0],
(&tbl[0]+sizeof(tbl)/sizeof(tbl[0])) etc

On 3/9/2011 11:12 AM, Angus wrote:
> On Mar 9, 2:28 pm, Victor Bazarov<v.baza...@comcast.invalid> wrote:
>> On 3/9/2011 8:48 AM, Angus wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>> I have had a go as below. But there is a problem if lookup value is
>>> smaller than any code in first column. What am I doing wrong? I
>>> assume my predicate is not quite correct?
>>
>>> #pragma warning(disable: 4786)
>>
>>> #include<iostream>
>>> #include<algorithm>
>>
>>> using namespace std;
>>
>>> struct errorinfo
>>> {
>>> errorinfo() : category(0), error(0) {}
>>> int category;
>>> int error;
>>> };
>>
>>> bool lessthanrow1(const int (&arr)[3], const int other)
>>> {
>>> return arr[0]< other;
>>> }
>>
>>> bool maperror2code(const int bw_error, errorinfo& csta_error)
>>> {
>>> const int cols = 3;
>>> //in real life much bigger array.
>>> static const int tbl[6][cols] = {
>>> 1000, 10, 0,
>>> 1001, 11, 1,
>>> 1200, 12, 2,
>>> 4002, 13, 3,
>>> 8090, 14, 4,
>>> 121105, 15, 5
>>> };
>>
>>> int tblsize = sizeof(tbl) /( sizeof(int) * cols);
>>
>>> int* result = (int*)lower_bound(tbl, tbl+tblsize, bw_error,
>>> lessthanrow1);
>>
>> Microsoft C++ 2008 and Comeau C++ (online) refuse to compile the line
>> above. How did you manage to run your program (if you did)? What
>> compiler allows you to use 'tbl' and 'tbl+tblsize' for the first and the
>> second arguments of 'lower_bound'?
>> [..]
>
> That works on VC++ v6. Otherwise can use lower_bound(&tbl[0],
> (&tbl[0]+sizeof(tbl)/sizeof(tbl[0])) etc

That doesn't work either. You're using a compiler that was released
before the original language standard. That compiler has enormous
problems with templates. I seriously doubt you're going to be
successful in learning the language and the standard library if you
continue using the compiler released so long ago. Not to mention type
casts like that.

Get yourself at least somewhat up to date VC++ 2010 Express Edition.
It's free. And get a good book on the standard library. Nicolai
Josuttis' work is recommended highly.

Good luck!

V
--
I do not respond to top-posted replies, please don't ask