[GitHub] [arrow] jorgecarleitao commented on pull request #7809: ARROW-9534: [Rust] [DataFusion] Add functions to create literal expressions

[GitBox <gi...@apache.org>]

jorgecarleitao commented on pull request #7809:
URL: https://github.com/apache/arrow/pull/7809#issuecomment-661276604


   Nice! I just needed this in my ballista's PR!
   
   following [this SO answer](https://stackoverflow.com/a/40776087/931303), what do you think of
   
   ```
   trait Literal {
       fn lit(&self) -> ScalarValue;
   }
   
   impl Literal for i32 {
       fn lit(&self) -> ScalarValue {
           ScalarValue::Int(self.clone())
       }
   }
   impl Literal for bool {
       fn lit(&self) -> ScalarValue {
           ScalarValue::Boolean(self.clone())
       }
   }
   
   fn lit<T: Literal>(n: T) -> ScalarValue {
       n.lit()
   }
   
   # usage:
   # lit(2);
   # lit(true);
   ```
   
   this way, the user does not have to import nor remember the value's type; they can just call `lit`. It seems to be a common pattern in rust.
   


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