I was wondering if anyone had design advice on this. . . . I am
doing some mathematical operations looking at different metrics for
data (in objects) I have captured. The object class has several data
attributes, say: metric1, metric2, . . . metricN. These are different
metrics on which I am running statistics.
There are a number of operations I have to do on these objects for
each metric separately: sort, group (i.e., group a list of objects
based on a metric), etc. I understand the very basics of C++ template
functions, overloading, etc. However, I cannot figure out a way to
design a generic function to sort by each single attribute. So, I end
up with functions like: sort_by_metric1 , sort_by_metric2 , . . .
sort_by_metricN .
Is there a way to avoid so many nearly-duplicative functions? For
example, is there a way in the function call to tell the function what
metric I want to sort by? This would allow me to use one, generic
function vice a bunch of nearly-duplicative ones.
I hope this is clear. If not, please let me know, and I will
attempt to clarify.
Thanks, Alan 5 1377
Alan wrote:
....
Is there a way to avoid so many nearly-duplicative functions?
You can use pointer to member as a parameter to your comparison function
for sorting.
Look up "pointer to member" in your fav C++ book - if you have further
questions, post again.
BTW - pointer to member may be a template parameter OR a value
parameter. It probably makes little difference.
Another wat is to code up different "getter" functions that get
different metrics and use those functions in your sort parameters.
Alan wrote:
I was wondering if anyone had design advice on this. . . . I am
doing some mathematical operations looking at different metrics for
data (in objects) I have captured. The object class has several data
attributes, say: metric1, metric2, . . . metricN. These are different
metrics on which I am running statistics.
Something like
#include <vector>
struct object {
double metric1, metric2 ... metricN;
}
....
std::vector<obj ectdata;
.... insert objects into data.
There are a number of operations I have to do on these objects for
each metric separately: sort, group (i.e., group a list of objects
based on a metric), etc. I understand the very basics of C++ template
functions, overloading, etc. However, I cannot figure out a way to
design a generic function to sort by each single attribute. So, I end
up with functions like: sort_by_metric1 , sort_by_metric2 , . . .
sort_by_metricN .
#include <algorithm>
#include <functional>
class less_metric1 : std::binary_fun ction<object, object, bool>{
public:
return_type operator()(cons t object& a, const object& b) {
return a.metric1 < b.metric1;
}
}
....
std::sort(data. begin(), data.end(), less_metric1()) ;
Is there a way to avoid so many nearly-duplicative functions? For
example, is there a way in the function call to tell the function what
metric I want to sort by? This would allow me to use one, generic
function vice a bunch of nearly-duplicative ones.
This is the purpose of templates.
--
rbh
Thank you. This was very helpful. Alan
On Jun 16, 10:33 pm, Alan <jalantho...@ve rizon.netwrote:
Thank you. This was very helpful. Alan
Robert,
I do not really understand what the line
return_type operator()(cons t object& a, const object& b)
does in your definition of the binary function. Can you explain?
I think I understand the rest now. Thank you for the suggestion.
Alan
Never mind. I found some information and discovered on another
thread that I should use "result_typ e."
Thanks again, Alan This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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