Mixing
C++ Loop and Compare Numbered Variables
I have a structure with similarly named variables such as
char c1;
char c2;
char c3;
char c4;
char c5;
char c6;
char c7;
char c8;
What I need is a loop that compares an input with each.
//Something Like
for(int i = 1; i <= 8; i++) {
if(compared == foo->c(i)) {
return compared;
}
}
Right now I have a long list of if and elses. I cannot change the struct unfortunately.
If the long string of if/elses are the most effective way of doing it (performance not how good the code looks) then Ill just keep it like that.
I basically want a loop that changes the variable name that I am currently comparing to make the code less messy and hopefully faster.
c++
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
add a comment |
I have a structure with similarly named variables such as
char c1;
char c2;
char c3;
char c4;
char c5;
char c6;
char c7;
char c8;
What I need is a loop that compares an input with each.
//Something Like
for(int i = 1; i <= 8; i++) {
if(compared == foo->c(i)) {
return compared;
}
}
Right now I have a long list of if and elses. I cannot change the struct unfortunately.
If the long string of if/elses are the most effective way of doing it (performance not how good the code looks) then Ill just keep it like that.
I basically want a loop that changes the variable name that I am currently comparing to make the code less messy and hopefully faster.
c++
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
7
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
2
Depending on the problem/code an array likechar c[8]might better fit your needs. Take care, array indizes start at 0, soc1would then bec[0].
– Werner Henze
Nov 19 '18 at 14:59
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
1
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12
add a comment |
I have a structure with similarly named variables such as
char c1;
char c2;
char c3;
char c4;
char c5;
char c6;
char c7;
char c8;
What I need is a loop that compares an input with each.
//Something Like
for(int i = 1; i <= 8; i++) {
if(compared == foo->c(i)) {
return compared;
}
}
Right now I have a long list of if and elses. I cannot change the struct unfortunately.
If the long string of if/elses are the most effective way of doing it (performance not how good the code looks) then Ill just keep it like that.
I basically want a loop that changes the variable name that I am currently comparing to make the code less messy and hopefully faster.
c++
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
I have a structure with similarly named variables such as
char c1;
char c2;
char c3;
char c4;
char c5;
char c6;
char c7;
char c8;
What I need is a loop that compares an input with each.
//Something Like
for(int i = 1; i <= 8; i++) {
if(compared == foo->c(i)) {
return compared;
}
}
Right now I have a long list of if and elses. I cannot change the struct unfortunately.
If the long string of if/elses are the most effective way of doing it (performance not how good the code looks) then Ill just keep it like that.
I basically want a loop that changes the variable name that I am currently comparing to make the code less messy and hopefully faster.
c++
c++
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
edited Nov 20 '18 at 10:46
gsamaras
50.6k2399186
50.6k2399186
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
asked Nov 19 '18 at 14:57
Cristian Camilo Cabrera
5516
5516
7
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
2
Depending on the problem/code an array likechar c[8]might better fit your needs. Take care, array indizes start at 0, soc1would then bec[0].
– Werner Henze
Nov 19 '18 at 14:59
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
1
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12
add a comment |
7
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
2
Depending on the problem/code an array likechar c[8]might better fit your needs. Take care, array indizes start at 0, soc1would then bec[0].
– Werner Henze
Nov 19 '18 at 14:59
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
1
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12
7
7
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
2
2
Depending on the problem/code an array like
char c[8] might better fit your needs. Take care, array indizes start at 0, so c1 would then be c[0].– Werner Henze
Nov 19 '18 at 14:59
Depending on the problem/code an array like
char c[8] might better fit your needs. Take care, array indizes start at 0, so c1 would then be c[0].– Werner Henze
Nov 19 '18 at 14:59
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
1
1
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12
add a comment |
2 Answers
2
active
oldest
votes
Well, since you can't change the structure, you can avoid some repetition and work around the requirment by using an array of pointers to the fields:
char const * c_ptr = {
&foo->c1, &foo->c2, &foo->c3, /* ... */, &foo->c8
};
Making your loop into this:
for(int i = 0; i < 8; ++i) {
if(compared == *c_ptr[i]) {
return compared;
}
}
But really, try to push for changing the structure if at all possible.
An alternative option, given this is C++, is to use pointers to members. Which has the added benefit of making the array constexpr (known entirely at compile time). So for instance, this code ...
static constexpr char Foo:: *c_ptr = {
&Foo::c1, &Foo::c2, &Foo::c3, &Foo::c4,
&Foo::c5, &Foo::c6, &Foo::c7, &Foo::c8
};
for(int i = 0; i < 8; ++i) {
if(compared == foo->*c_ptr[i]) {
return compared;
}
}
... can be successfully optimized to an unrolled loop, equivalent to a sequence of branches.
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
add a comment |
You can use a std::reference_wrapper with char as the template parameter.
Then your will code will look like this:
#include <functional>
using charRef = std::reference_wrapper<char>;
struct Foo {
char c1, c2, c3, c4, c5, c6, c7, c8;
};
char processFoo(Foo& f, char compared) {
charRef CR = {f.c1, f.c2, f.c3, f.c4, f.c5, f.c6, f.c7, f.c8};
for(int i = 0; i < 8; ++i) {
if(compared == CR[i]) {
return compared;
}
}
return '';
}
answered Nov 20 '18 at 10:44
P.W
11.4k3842
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Well, since you can't change the structure, you can avoid some repetition and work around the requirment by using an array of pointers to the fields:
char const * c_ptr = {
&foo->c1, &foo->c2, &foo->c3, /* ... */, &foo->c8
};
Making your loop into this:
for(int i = 0; i < 8; ++i) {
if(compared == *c_ptr[i]) {
return compared;
}
}
But really, try to push for changing the structure if at all possible.
An alternative option, given this is C++, is to use pointers to members. Which has the added benefit of making the array constexpr (known entirely at compile time). So for instance, this code ...
static constexpr char Foo:: *c_ptr = {
&Foo::c1, &Foo::c2, &Foo::c3, &Foo::c4,
&Foo::c5, &Foo::c6, &Foo::c7, &Foo::c8
};
for(int i = 0; i < 8; ++i) {
if(compared == foo->*c_ptr[i]) {
return compared;
}
}
... can be successfully optimized to an unrolled loop, equivalent to a sequence of branches.
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
add a comment |
Well, since you can't change the structure, you can avoid some repetition and work around the requirment by using an array of pointers to the fields:
char const * c_ptr = {
&foo->c1, &foo->c2, &foo->c3, /* ... */, &foo->c8
};
Making your loop into this:
for(int i = 0; i < 8; ++i) {
if(compared == *c_ptr[i]) {
return compared;
}
}
But really, try to push for changing the structure if at all possible.
An alternative option, given this is C++, is to use pointers to members. Which has the added benefit of making the array constexpr (known entirely at compile time). So for instance, this code ...
static constexpr char Foo:: *c_ptr = {
&Foo::c1, &Foo::c2, &Foo::c3, &Foo::c4,
&Foo::c5, &Foo::c6, &Foo::c7, &Foo::c8
};
for(int i = 0; i < 8; ++i) {
if(compared == foo->*c_ptr[i]) {
return compared;
}
}
... can be successfully optimized to an unrolled loop, equivalent to a sequence of branches.
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
add a comment |
Well, since you can't change the structure, you can avoid some repetition and work around the requirment by using an array of pointers to the fields:
char const * c_ptr = {
&foo->c1, &foo->c2, &foo->c3, /* ... */, &foo->c8
};
Making your loop into this:
for(int i = 0; i < 8; ++i) {
if(compared == *c_ptr[i]) {
return compared;
}
}
But really, try to push for changing the structure if at all possible.
An alternative option, given this is C++, is to use pointers to members. Which has the added benefit of making the array constexpr (known entirely at compile time). So for instance, this code ...
static constexpr char Foo:: *c_ptr = {
&Foo::c1, &Foo::c2, &Foo::c3, &Foo::c4,
&Foo::c5, &Foo::c6, &Foo::c7, &Foo::c8
};
for(int i = 0; i < 8; ++i) {
if(compared == foo->*c_ptr[i]) {
return compared;
}
}
... can be successfully optimized to an unrolled loop, equivalent to a sequence of branches.
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
Well, since you can't change the structure, you can avoid some repetition and work around the requirment by using an array of pointers to the fields:
char const * c_ptr = {
&foo->c1, &foo->c2, &foo->c3, /* ... */, &foo->c8
};
Making your loop into this:
for(int i = 0; i < 8; ++i) {
if(compared == *c_ptr[i]) {
return compared;
}
}
But really, try to push for changing the structure if at all possible.
An alternative option, given this is C++, is to use pointers to members. Which has the added benefit of making the array constexpr (known entirely at compile time). So for instance, this code ...
static constexpr char Foo:: *c_ptr = {
&Foo::c1, &Foo::c2, &Foo::c3, &Foo::c4,
&Foo::c5, &Foo::c6, &Foo::c7, &Foo::c8
};
for(int i = 0; i < 8; ++i) {
if(compared == foo->*c_ptr[i]) {
return compared;
}
}
... can be successfully optimized to an unrolled loop, equivalent to a sequence of branches.
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
edited Nov 20 '18 at 6:16
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
answered Nov 19 '18 at 15:06
StoryTeller
93.9k12187253
93.9k12187253
add a comment |
add a comment |
You can use a std::reference_wrapper with char as the template parameter.
Then your will code will look like this:
#include <functional>
using charRef = std::reference_wrapper<char>;
struct Foo {
char c1, c2, c3, c4, c5, c6, c7, c8;
};
char processFoo(Foo& f, char compared) {
charRef CR = {f.c1, f.c2, f.c3, f.c4, f.c5, f.c6, f.c7, f.c8};
for(int i = 0; i < 8; ++i) {
if(compared == CR[i]) {
return compared;
}
}
return '';
}
answered Nov 20 '18 at 10:44
P.W
11.4k3842
add a comment |
You can use a std::reference_wrapper with char as the template parameter.
Then your will code will look like this:
#include <functional>
using charRef = std::reference_wrapper<char>;
struct Foo {
char c1, c2, c3, c4, c5, c6, c7, c8;
};
char processFoo(Foo& f, char compared) {
charRef CR = {f.c1, f.c2, f.c3, f.c4, f.c5, f.c6, f.c7, f.c8};
for(int i = 0; i < 8; ++i) {
if(compared == CR[i]) {
return compared;
}
}
return '';
}
answered Nov 20 '18 at 10:44
P.W
11.4k3842
add a comment |
You can use a std::reference_wrapper with char as the template parameter.
Then your will code will look like this:
#include <functional>
using charRef = std::reference_wrapper<char>;
struct Foo {
char c1, c2, c3, c4, c5, c6, c7, c8;
};
char processFoo(Foo& f, char compared) {
charRef CR = {f.c1, f.c2, f.c3, f.c4, f.c5, f.c6, f.c7, f.c8};
for(int i = 0; i < 8; ++i) {
if(compared == CR[i]) {
return compared;
}
}
return '';
}
answered Nov 20 '18 at 10:44
P.W
11.4k3842
You can use a std::reference_wrapper with char as the template parameter.
Then your will code will look like this:
#include <functional>
using charRef = std::reference_wrapper<char>;
struct Foo {
char c1, c2, c3, c4, c5, c6, c7, c8;
};
char processFoo(Foo& f, char compared) {
charRef CR = {f.c1, f.c2, f.c3, f.c4, f.c5, f.c6, f.c7, f.c8};
for(int i = 0; i < 8; ++i) {
if(compared == CR[i]) {
return compared;
}
}
return '';
}
answered Nov 20 '18 at 10:44
P.W
11.4k3842
edited Nov 20 '18 at 11:57
answered Nov 20 '18 at 10:44
P.W
11.4k3842
answered Nov 20 '18 at 10:44
P.W
11.4k3842
answered Nov 20 '18 at 10:44
P.W
11.4k3842
11.4k3842
add a comment |
add a comment |
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7
If all those elements are of the same type, why not use an array instead? Or a map? What's the purpose of those similarly named members?
– Some programmer dude
Nov 19 '18 at 14:58
2
Depending on the problem/code an array like
char c[8]might better fit your needs. Take care, array indizes start at 0, soc1would then bec[0].– Werner Henze
Nov 19 '18 at 14:59
There is no way to do what you're asking without reflection, which C++ does not support.
– Arnav Borborah
Nov 19 '18 at 15:03
1
Maybe this: stackoverflow.com/a/25953607/487892 if you can't change the poor design decision.
– drescherjm
Nov 19 '18 at 15:04
@Someprogrammerdude Yeah, but the struct was made years ago and is compliant to a standard so I definitely wont be able to change it to anything else. Even if it would be efficient.
– Cristian Camilo Cabrera
Nov 19 '18 at 15:12