Databases
StackOverflow2013
Postsdbo
PODeclaring variables in the arguments to a function in C
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PODeclaring variables in the arguments to a function in C
    primarykey
    data
    text
    <p>I have a sort of bizarre wish; I don't know if any compiler or language extension out there allows this.</p> <p>I want to be able to declare variables inside a function invocation, like this:</p> <pre><code>int test(int *out_p) { *out_p = 5; return 1; } int main() { if (int ret = test(int &amp;var)) { // int var declared inside function invocation fprintf(stderr, "var = %d\n", var); // var in scope here } return 0; } </code></pre> <p>because then the scoping of var follows the scoping of ret. For another example (from a project I'm working on now), I have </p> <pre><code>cmd_s = readline(); int x, y, dX, dY, symA, symB; if (sscanf(cmd_s, "placeDomino:%d %d atX:%d y:%d dX:%d dY:%d", &amp;symA, &amp;symB, &amp;x, &amp;y, &amp;dX, &amp;dY) == 6) { do_complicated_stuff(symA, symB, x, y, dX, dY); } else if (sscanf(cmd_s, "placeAtX:%d y:%d dX:%d dY:%d", &amp;x, &amp;y, &amp;dX, &amp;dY) == 4) { do_stuff(x, y, dX, dY); /* symA, symB are in scope but uninitialized :-( so I can accidentally * use their values and the compiler will let me */ } </code></pre> <p>and I would prefer to write</p> <pre><code>cmd_s = readline(); if (sscanf(cmd_s, "placeDomino:%d %d atX:%d y:%d dX:%d dY:%d", int &amp;symA, int &amp;symB, int &amp;x, int &amp;y, int &amp;dX, int &amp;dY) == 6) { do_complicated_stuff(symA, symB, x, y, dX, dY); } else if (sscanf(cmd_s, "placeAtX:%d y:%d dX:%d dY:%d", int &amp;x, int &amp;y, int &amp;dX, int &amp;dY) == 4) { do_stuff(x, y, dX, dY); /* Now symA, symB are out of scope here and I can't * accidentally use their uninitialized values */ } </code></pre> <p>My question is, does any compiler support this? Does gcc support it if I rub it the right way? Is there a C or C++ (draft) spec that has this?</p> <p>Edit: just realized that in my first code example, my declaration of int ret is also no good in C99; I guess I'm spoiled by for loops. I want that feature too; imagine </p> <pre><code>while(int condition = check_condition()) { switch(condition) { ... } } </code></pre> <p>or something like that. </p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USzmccord
    1. USzmccord
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PODeclaring variables in the arguments to a function in C
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PODeclaring variables in the arguments to a function in C
      1. This table or related slice is empty.
      1. VTUpMod
    1. COWould you sacrifice clarity for brevity?
      singulars
      1. PODeclaring variables in the arguments to a function in C
      1. USvulkanino
    2. COI did say "bizarre wish" :-p I generally find brevity improves clarity; this is why I prefer to use idioms that afford me brevity where I can find them. I'm probably out of luck on this particular idiom, though.
      singulars
      1. PODeclaring variables in the arguments to a function in C
      1. USzmccord
    3. CO@vulkanino Of course. Do you have any idea how much keyboards cost these days? We are talking of at least $10 every decade in keyboard costs! Clearly, wear and tear of the keyboard should be the primary concern of any successful programmer.
      singulars
      1. PODeclaring variables in the arguments to a function in C
      1. USLundin
 

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