Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>No. The return type of a C++ function can only vary based on explicit template parameters or the <em>types</em> of its arguments. It cannot vary based on the <em>value</em> of its arguments.</p> <p>However, you can use various techniques to create a type that is the union of several other types. Unfortunately this won't necessarily help you here, as one such technique is void * itself, and getting back to the original type will be a pain.</p> <p>However, by turning the problem inside out you may get what you want. I imagine you'd want to use the code you posted as something like, for example:</p> <pre><code>void bitmap_operation(void *data, int depth, int width, int height) { some_magical_type p_pixels = returnPointer(data, depth); for (int x = 0; x &lt; width; x++) for (int y = 0; y &lt; width; y++) p_pixels[y*width+x] = some_operation(p_pixels[y*width+x]); } </code></pre> <p>Because C++ needs to know the type of p_pixels at compile time, this won't work as-is. But what we can do is make bitmap_operation itself be a template, then wrap it with a switch based on the depth:</p> <pre><code>template&lt;typename PixelType&gt; void bitmap_operation_impl(void *data, int width, int height) { PixelType *p_pixels = (PixelType *)data; for (int x = 0; x &lt; width; x++) for (int y = 0; y &lt; width; y++) p_pixels[y*width+x] = some_operation(p_pixels[y*width+x]); } void bitmap_operation(void *data, int depth, int width, int height) { if (depth == 8) bitmap_operation_impl&lt;uint8_t&gt;(data, width, height); else if (depth == 16) bitmap_operation_impl&lt;uint16_t&gt;(data, width, height); else if (depth == 32) bitmap_operation_impl&lt;uint32_t&gt;(data, width, height); else assert(!"Impossible depth!"); } </code></pre> <p>Now the compiler will automatically generate three implementations for bitmap_operation_impl for you.</p>
    singulars
    1. This table or related slice is empty.
    1. POReturning different data type depending on the data (C++)
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USbdonlan
    1. USbdonlan
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POReturning different data type depending on the data (C++)
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COIn C#, you can return an object type, and cast it to your desired object (provided you know the type). Or you can use generics. Can you do something similar in c++?
      singulars
      1. PO
      1. USRobert Harvey
    2. COThe closest C++ has to an object type is void *. There's also boost's variant type.
      singulars
      1. PO
      1. USbdonlan
    3. COI guess i would use boost variant too.
      singulars
      1. PO
      1. USJohannes Schaub - litb
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload