STL Iterators

[Christian Christmann]

Hi,

my program contains a class with a STL vector std::vector<int> data and an
integer variable "currentbit" which indicates the current position while
traversing the vector.

In my function first() I'm searching for a particular value and save the
position in "currentbit". Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

but the compiler complains:

invalid type argument of `unary *'

What's wrong? How can I assing an iterator to a particular position in the
vector?

Thanks
Chris

 

[Andrew McDonagh]

Hi,

my program contains a class with a STL vector std::vector<int> data and an
integer variable "currentbit" which indicates the current position while
traversing the vector.

In my function first() I'm searching for a particular value and save the
position in "currentbit". Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

but the compiler complains:

invalid type argument of `unary *'

What's wrong? How can I assing an iterator to a particular position in the
vector?

Thanks
Chris

its complaining because *data[currentBit+1] is not an iterator.

It would be simpler to declare currentBit to be an Iterator rather than
an (I'm assuming) int.

so your first() method would use iterators to loop through the vector to
find the specific element and when found, instead of assigning an int
value to currentBit, you would: currentBit = iter;

Then when your next() method is called, you can simply do

return currentBit++;

Andrew

 

[Christian Christmann]

In my function first() I'm searching for a particular value and save the
position in "currentbit". Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

its complaining because *data[currentBit+1] is not an iterator.

It would be simpler to declare currentBit to be an Iterator rather than an
(I'm assuming) int.

Thank you for your suggestion. That's a good idea but I need currentBit as
int for some other calculations. So I don't want to change it to an
iterator.

Is there another way to assign an iterator to an particular int array
position?

Andrew

Chris

 

[Duane Hebert]

In my function first() I'm searching for a particular value and save the
position in "currentbit". Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

its complaining because *data[currentBit+1] is not an iterator.

What's the *data for?
Have you tried

vector<int>::iterator iter = data[currentbit + 1];
or
vector<int>::iterator iter = data.begin() + (currentbit + 1);

 

[Christian Christmann]

In my function first() I'm searching for a particular value and save
the position in "currentbit". Within another function next() I'd like
to continue searching beginning in the vector at position
"currentbit". My idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

its complaining because *data[currentBit+1] is not an iterator.

What's the *data for?
Have you tried

vector<int>::iterator iter = data.begin() + (currentbit + 1);

Thank you very much, this works

Chris

 

[Ioannis Vranos]

Hi,

my program contains a class with a STL vector std::vector<int> data and an
integer variable "currentbit" which indicates the current position while
traversing the vector.


In my function first() I'm searching for a particular value and save the
position in "currentbit".

Better use std::search family.

Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

If you want to continue from currentbit+1, and data is your vector<int>,
you can do:

vector<int>::const_iterator iter = data.begin()+currentbit+1;

 

[Ioannis Vranos]

Better use std::find family.

Within another function next() I'd like to
continue searching beginning in the vector at position "currentbit". My
idea was to create an iterator:

vector<int>::const_iterator iter = *data[currentbit+1]

If you want to continue from currentbit+1, and data is your vector<int>,
you can do:

vector<int>::const_iterator iter = data.begin()+currentbit+1;

 

[Duane Hebert]

Thank you very much, this works

Should work with const_iterator as well. I forgot it in
the example.

 

[Christian Christmann]

Should work with const_iterator as well. I forgot it in the example.

Thanks, I used the const_iterator