Documentation for switch statements with no control expression

[gabehollombe]

Added the following to the docs in the Switch section:

Switch statements can also be used without a control expression, turning them in to a cleaner alternative to if/else chains.

score = 76
grade = switch
when score < 60 then 'F'
when score < 70 then 'D'
when score < 80 then 'C'
when score < 90 then 'B'
else 'A'

grade == 'C'

[jashkenas]

While legal, I think this would usually be an abuse of switch. Why not just use if/else for this? Because you prefer to type when instead of else if ? Performance?

[marcandre]

+1.

A 'switch' statement is very descriptive: from the get go you know that at most one of many conditions will take place. I find it more expressive and harder to get confused. There's also only one way to indent it, compared to nested else-if that could be indented in different ways.

Other argument: what else could/should @gabehollombe 's code be translated to?

Finally: it works now, so for compatibility... it should be supported in the future too.

[gabehollombe]

Why not just use if/else for this? Because you prefer to type when
instead of else if ? Performance?

I feel the switch format reads a lot nicer. Less keywords (if/else) on the
screen makes the intent of the assignment easier to parse, for my brain at
least.

On Fri, Jul 6, 2012 at 9:36 PM, Jeremy Ashkenas <
[email protected]

wrote:

While legal, I think this would usually be an abuse of switch. Why not
just use if/else for this? Because you prefer to type when instead of
else if ? Performance?

---

Reply to this email directly or view it on GitHub:
#2417 (comment)

[marcandre]

PS: Forgot to mention that Ruby supports this style of switch too...

[sergeych]

+1

this is cleaner and more convenient way than 'else if' chains. Less noise, more sense. Pls include ;) 'Least surprising' principle, as in ruby, where this construction is widely used (while ruby hardly misses chained comaprisons ;)).

[epidemian]

+1 for documenting empty switch statements. -1 for this particular example. I'd prefer it written as:

score = 76
grade = switch
  when score < 60 then 'F'
  when score < 70 then 'D'
  when score < 80 then 'C'
  when score < 90 then 'B'
  else 'A'

It can also be written as a cascade of return ... if ... if you put it inside a function (see this is SO question for reference)

[justinclift]

@epidemian That does look a lot clearer than the initial proposal by @gabehollombe. Shows the common usage for ranges very nicely.

@gabehollombe Any objections to using @epidemian's approach instead?

[gabehollombe]

No objections at all. =-)

On Sun, Oct 7, 2012 at 5:33 AM, Justin Clift [email protected]:

@epidemian https://github.com/epidemian That does look a lot clearer
than the initial proposal by @gabehollombehttps://github.com/gabehollombe.
Shows the common usage for ranges very nicely.

@gabehollombe https://github.com/gabehollombe Any objections to using
@epidemian https://github.com/epidemian's approach instead?

—
Reply to this email directly or view it on GitHubhttps://github.com//pull/2417#issuecomment-9200932.

[justinclift]

@gabehollombe Heh, cool. Any chance you can update the pull request? :)

[marcandre]

👏