6 ms·

> "Specifically, a warning is issued for if, else, while, and for clauses with a guarded statement that does not use braces, followed by an unguarded statement

> "Specifically, a warning is issued for if, else, while, and for clauses with a guarded statement that does not use braces, followed by an unguarded statement with the same indentation." > "The warning is not issued for code involving multiline preprocessor logic ... The warning is not issued after a @code{#line} directive, since this typically indicates autogenerated code" Seems like a good thing to have, and pretty conservative about not causing false positives. In particular, constructs like double-iteration should be fine: for(y=0; y<ymax; y++) for(x=0; x<xmax; x++) { //... } Which I checked because I like this construct and people very rarely think about it.

noobie 11y ago
I apologize for the stupidity of my question but shouldn't that be for(y=0; y<ymax; y++) { for(x=0; x<xmax; x++) { //... } } ? Edit: Oh, I get it, {} are only "mandatory" if we have more than one instruction, the second for loop gets counted as one instruction and hence the omitting of {}. Thanks!
- avar 11y ago
  No, the two mean the same thing in C, e.g.: if (x) y; Is the same as: if (x) { y; }
  - Macha 11y ago
    Just in case anyone who has never used C (or Java, or C# etc etc) is confused, it's not the indentation that is causing this meaning here: if (x) y; also has the same meaning.
- recursive 11y ago
  Why would it be? Certainly not for readability. I think it was posted as intended.
- Sir_Cmpwn 11y ago
  It works without the additional braces. Consider this: for (i=0;i<imax;i++) printf("%d\n", i); You can omit the braces if the body of the loop is a single block, just like an if statement. You can also do this: if (a == b) if (b == c) { do_thing(); } Same deal with the for loop. The nested loop is a single block.
- deleted 11y ago
  [deleted]
- halosghost 11y ago
  In C, control flow like if, for, while, do, else, etc., take the rest of the line of code (i.e., till the next semi-colon) and runs it under the conditions of the clause. braces—{}—allow you to take multiple lines of code and have them be guarded at the same time rather than having to repeat the condition. GP is taking advantage of the fact that the next for clause will be considered a single statement, and therefore the second set of braces are not technically needed. However, omitting braces for single-line snippets has caused plenty of havoc in the past (cf. Apple's gotofail). Some would say it is better to always include braces in control flow.
- jimrandomh 11y ago
  If I were doing it that way, I wouldn't give the outer blocks' curly braces their own lines. For example in C#, where pretty much every file has a single "namespace" block containing a single "class" block, I write it as: namespace SomeNamespace { class SomeClass { //... }} Which avoids having shifted the whole file an extra indent level to the right. But I haven't seen anyone else doing this.
  - Avshalom 11y ago
    I'm not writing C# but yeah: AS3 and Java both have the Package{class{ two-step before you actually write any code. I don't even indent inside class: package{ class{ main{ now we indent } }}
    - threeseed 11y ago
      You don't indent after a package e.g. https://github.com/apache/spark/blob/master/core/src/main/java/org/apache/spark/JavaSparkListener.java https://github.com/apache/spark/blob/master/core/src/main/ja... And it's fair enough to indent with a main since it is so infrequent. Ideally you only have one main entry point.
JoshTriplett 11y ago
That pattern still seems like obfuscation to me. Why not indent the inner for loop, to make the control flow more obvious? For instance, consider how "break" or "continue" inside the braces would work.
- contravariant 11y ago
  I don't see how 'continue' would be confusing, it would stop the current calculation and start the next one, same as with normal loops. The behaviour of 'break' might be confusing but then that's always the case in nested loops, no matter how you notate them.
  - wasyl 11y ago
    I would argue that `break` intuitively makes you go back an indent, so if you don't indent after the first `for`, one can assume `break` just exits both loops (goes back from lvl 1 to lvl 0 indent)
    - jimrandomh 11y ago
      This doesn't quite work, since break skips over if statements (and most breaks have at least one if statement around them). So you have to look glance at the keyword at the elbow of each indent anyways, to know where it's going.
- jimrandomh 11y ago
  The reason for doing it that way, is to emphasize when two loops together are conceptually iterating over a single thing, and have some symmetry, like iterating over the cells in a 2D grid. It makes it possible to line up the elements of the two loops, emphasizing the similar structure. I agree that it would be very bad form to use "break" inside a block like that. But in the cases where this construct applies, it would still be bad form to break if the outer block had curly braces and indentation, because skipping the rest of a row isn't a natural operation in the sort of way that skipping the rest of a collection is.
chris_wot 11y ago
Ew! That's not any better at all... Man's gotta have an opinion. At least C doesn't have optional semi-colons.
cnvogel 11y ago
While I understand that it's mostly a question of aesthetics, I don't like this also because it might break the expected semantics of continue/break in such a loop. When I iterate over things more complex than a single variable where the conditions in a for() would become ugly, I tend to put the domain-specific "increment" into a small static function: static int next_pixel(*x, *y, width, height) { (*x)++; ... if (last pixel...) return 0; return 1; } /* later on... */ do { /* do something with coordinates x, y */ } while (next_pixel(&x, &y, WIDTH, HEIGHT)); This is, of course, not only restricted to 2D arrays, but could cover walking of a tree or a filesystem...
Spl3en 11y ago
What about this ? for(y=0; y<ymax; y++) { for(x=0; x<xmax; x++) { //... } }
eru 11y ago
I'd put the two loop-headers on the same line in that case.
thiht 11y ago
If I see this, I'll immediately think it's a bug, the difference between x and y is not even obvious at first sight, it looks like the line was duplicated accidentally.

noobie 11y ago

I apologize for the stupidity of my question but shouldn't that be for(y=0; y<ymax; y++) { for(x=0; x<xmax; x++) { //... } } ? Edit: Oh, I get it, {} are only "mandatory" if we have more than one instruction, the second for loop gets counted as one instruction and hence the omitting of {}. Thanks!

avar 11y ago
No, the two mean the same thing in C, e.g.: if (x) y; Is the same as: if (x) { y; }
- Macha 11y ago
  Just in case anyone who has never used C (or Java, or C# etc etc) is confused, it's not the indentation that is causing this meaning here: if (x) y; also has the same meaning.
recursive 11y ago
Why would it be? Certainly not for readability. I think it was posted as intended.
Sir_Cmpwn 11y ago
It works without the additional braces. Consider this: for (i=0;i<imax;i++) printf("%d\n", i); You can omit the braces if the body of the loop is a single block, just like an if statement. You can also do this: if (a == b) if (b == c) { do_thing(); } Same deal with the for loop. The nested loop is a single block.
deleted 11y ago
[deleted]
halosghost 11y ago
In C, control flow like if, for, while, do, else, etc., take the rest of the line of code (i.e., till the next semi-colon) and runs it under the conditions of the clause. braces—{}—allow you to take multiple lines of code and have them be guarded at the same time rather than having to repeat the condition. GP is taking advantage of the fact that the next for clause will be considered a single statement, and therefore the second set of braces are not technically needed. However, omitting braces for single-line snippets has caused plenty of havoc in the past (cf. Apple's gotofail). Some would say it is better to always include braces in control flow.
jimrandomh 11y ago
If I were doing it that way, I wouldn't give the outer blocks' curly braces their own lines. For example in C#, where pretty much every file has a single "namespace" block containing a single "class" block, I write it as: namespace SomeNamespace { class SomeClass { //... }} Which avoids having shifted the whole file an extra indent level to the right. But I haven't seen anyone else doing this.
- Avshalom 11y ago
  I'm not writing C# but yeah: AS3 and Java both have the Package{class{ two-step before you actually write any code. I don't even indent inside class: package{ class{ main{ now we indent } }}
  - threeseed 11y ago
    You don't indent after a package e.g. https://github.com/apache/spark/blob/master/core/src/main/java/org/apache/spark/JavaSparkListener.java https://github.com/apache/spark/blob/master/core/src/main/ja... And it's fair enough to indent with a main since it is so infrequent. Ideally you only have one main entry point.

JoshTriplett 11y ago

That pattern still seems like obfuscation to me. Why not indent the inner for loop, to make the control flow more obvious? For instance, consider how "break" or "continue" inside the braces would work.

contravariant 11y ago
I don't see how 'continue' would be confusing, it would stop the current calculation and start the next one, same as with normal loops. The behaviour of 'break' might be confusing but then that's always the case in nested loops, no matter how you notate them.
- wasyl 11y ago
  I would argue that `break` intuitively makes you go back an indent, so if you don't indent after the first `for`, one can assume `break` just exits both loops (goes back from lvl 1 to lvl 0 indent)
  - jimrandomh 11y ago
    This doesn't quite work, since break skips over if statements (and most breaks have at least one if statement around them). So you have to look glance at the keyword at the elbow of each indent anyways, to know where it's going.
jimrandomh 11y ago
The reason for doing it that way, is to emphasize when two loops together are conceptually iterating over a single thing, and have some symmetry, like iterating over the cells in a 2D grid. It makes it possible to line up the elements of the two loops, emphasizing the similar structure. I agree that it would be very bad form to use "break" inside a block like that. But in the cases where this construct applies, it would still be bad form to break if the outer block had curly braces and indentation, because skipping the rest of a row isn't a natural operation in the sort of way that skipping the rest of a collection is.

chris_wot 11y ago

Ew! That's not any better at all... Man's gotta have an opinion. At least C doesn't have optional semi-colons.

cnvogel 11y ago

While I understand that it's mostly a question of aesthetics, I don't like this also because it might break the expected semantics of continue/break in such a loop. When I iterate over things more complex than a single variable where the conditions in a for() would become ugly, I tend to put the domain-specific "increment" into a small static function: static int next_pixel(*x, *y, width, height) { (*x)++; ... if (last pixel...) return 0; return 1; } /* later on... */ do { /* do something with coordinates x, y */ } while (next_pixel(&x, &y, WIDTH, HEIGHT)); This is, of course, not only restricted to 2D arrays, but could cover walking of a tree or a filesystem...

Spl3en 11y ago

What about this ? for(y=0; y<ymax; y++) { for(x=0; x<xmax; x++) { //... } }

eru 11y ago

I'd put the two loop-headers on the same line in that case.

thiht 11y ago

If I see this, I'll immediately think it's a bug, the difference between x and y is not even obvious at first sight, it looks like the line was duplicated accidentally.