# Branching or Exit Points : Quad Saga **URL:** \ **Category:** language design\ **Created:** [September 5, 2017, 3:03pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862 "2017-09-05T15:03:23Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![genieme](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@genieme](https://internals.rust-lang.org/u/genieme)\ **Post date:** [September 5, 2017, 3:03pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/1 "2017-09-05T15:03:23Z")
Branching or Exit Points : Quad Saga - Consistency : promotes simplicity - Simplicity : promotes easy learning. Names for the 4 functions : - fn branchOut() returns () - fn branchTo(Label) returns () - fn branchWith() returns Val - fn branchIf(BoolExp) returns () Syntaxes of the 4 Expressions : - break; or break (); - break 'label; - break val; - break if x \> y; ? we need ‘break if’ expression. ‘if’ is the filter for the exit point : exit iff true. Usage : inside ‘loop’ block loop { break if x \> y; // equivalent to js : while (x \> y) {… } … } loop { … // equivalent to js : do{ … } while (x \> y); break if x \> y; } loop { … // see ada-lang : ‘exit when’ syntax for an equivalent. // 2 or more can be placed anywhere in the the loop, scattered or not. break if x \> y; … } Note : that is a lot of flexibility and expressive powess. Yet the rust core team keeps it from us ?? 🙂 Please correct the wrong ?? 🙂 when teaching the branching concept to school students, leaving one component out is a disservice. they need complete understanding and practice of the concept. Please Help Us Out. THANKS. ---
**Author:** ![dtolnay](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/dtolnay/32/1447_2.png) [@dtolnay](https://internals.rust-lang.org/u/dtolnay)\ **Post date:** [September 5, 2017, 3:19pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/2 "2017-09-05T15:19:37Z")
What are some reasons to prefer `break if x > y` over `if x > y { break }`? ---
**Author:** ![genieme](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@genieme](https://internals.rust-lang.org/u/genieme)\ **Post date:** [September 5, 2017, 3:57pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/3 "2017-09-05T15:57:27Z")
@dtolnay the ‘if’ keyword is being used as a filter. we can get rid of if statement or expression, if need be we can get rid of while(){} statement or expression also I am trying to promote consistency, which may lower the learning curve barrier: ‘On Boarding’. And use match or loop expression or statement instead. less syntax -\> less to learn ---
**Author:** ![Diggsey](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/diggsey/32/6311_2.png) [@Diggsey](https://internals.rust-lang.org/u/Diggsey)\ **Post date:** [September 5, 2017, 4:09pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/4 "2017-09-05T16:09:29Z")
> the ‘if’ keyword is being used as a filter. that is a very arbitrary distinction to make, there's no real difference between the two constructs - you seem to be suggesting that the design of the AST is important for a beginner to the language. Are you sure you're not just arguing for this syntax because it reads more like natural language? > less syntax -\> less to learn So how does adding _more_ redundant syntax help? ---
**Author:** ![dtolnay](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/dtolnay/32/1447_2.png) [@dtolnay](https://internals.rust-lang.org/u/dtolnay)\ **Post date:** [September 5, 2017, 4:10pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/5 "2017-09-05T16:10:16Z")
To clarify, in your code is the behavior identical to `if x > y { break }`? ---
**Author:** ![genieme](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@genieme](https://internals.rust-lang.org/u/genieme)\ **Post date:** [September 5, 2017, 4:41pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/6 "2017-09-05T16:41:14Z")
@dtolnay and @Diggsey I am discussing the break exit points as a set of four entities. they are all related to the same concept : exit points. that is the consistency. ‘break if’ is the last one remaining. Yes its semaintics is equivalent to : if (x\>y) {break;} but that is not an exit-point or branching. - break; - break 5; - break 'label; - break if x \> y; CONSISTENCY 🙂 I personally do not use the while keyword. it is conditional repetition. and not that flexible at all. ‘loop’ keyword + ‘break if’ combine give great flexibility. see the many ways of using them in the original post. we can deprecate ‘while’ and ‘if’ statement altogether. one syntax in : two syntax out ---
**Author:** ![ExpHP](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/exphp/32/6208_2.png) [@ExpHP](https://internals.rust-lang.org/u/ExpHP)\ **Post date:** [September 5, 2017, 8:17pm UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/7 "2017-09-05T20:17:01Z")
> we can deprecate ‘while’ and ‘if’ statement altogether. While we're at it, we can deprecate `for` loops and block expressions too. And we can also get rid of bare `break`; best be explicit with `break if true`: ```rust // old rust let sorted = { let mut vec: Vec<_> = iter.collect(); vec.sort(); vec }; // new, idiomatic rust let sorted = loop { let mut vec: Vec<_> = iter.collect(); vec.sort(); break vec if true; }; ``` ---
**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/system/32/14092_2.png) [@system](https://internals.rust-lang.org/u/system)\ **Post date:** [March 25, 2019, 8:28am UTC](https://internals.rust-lang.org/t/branching-or-exit-points-quad-saga/5862/8 "2019-03-25T08:28:58Z")
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