[GitHub] pnowojski commented on a change in pull request #6700: [FLINK-10340][table] Add Cosh math function supported in Table API and SQL

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pnowojski commented on a change in pull request #6700: [FLINK-10340][table] Add Cosh math function supported in Table API and SQL
URL: https://github.com/apache/flink/pull/6700#discussion_r221537661
 
 

 ##########
 File path: docs/dev/table/functions.md
 ##########
 @@ -1274,6 +1274,17 @@ ATAN2(numeric1, numeric2)
       </td>
     </tr>
 
+    <tr>
+      <td>
+        {% highlight text %}
+COSH(numeric)
+{% endhighlight %}
+      </td>
+      <td>
+        <p>Returns the hyperbolic cosine of <i>numeric</i>. Return value type is DOUBLE.</p>
 
 Review comment:
   @xccui if you think using `<i>` is better I'm fine with that, I don't mind one way or the other.
   
   However I don't understand:
   
   > before reaching a consensus about the format and the internal implementation, I suggest to keep the current doc style, i.e., without mentioning the return type, for now.
   
   We are already following a convention that for all of the math functions we are dropping precision and returning `double`. What's the point of not documenting it?
   
   If you could guarantee me that we will document those return types lets say within a month, I would be fine with postponing it. However I don't believe something like that would happen, so I prefer to incrementally start adding this return type information right now. Later if someone will want, we can reformat the page. I do not see any downside to such incremental approach until that moment.
   
   > why still indicating the return type for each numeric function explicitly? How about adding a single note for that?
   
   since some of them can be implemented precisely (`abs`, `min`, `max`, `ceil`, ...), others can be for some variants (`power(DECIMAL, INT)`). We can state this general rule that functions returning `DOUBLE` are approximations, but we still need specific information for every function, whether it returns approximated (`DOUBLE`) or precise (`DECIMAL`) result. 
   

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