Comment by ngruhn

1 month ago

I can live with these negatives. What irritates me the most is the lack of if/else or guards or some kind of dedicated case-distinction on booleans. Pattern matching is great but for booleans it can be kinda verbose. E.g.

   case x < 0 {
     True -> ...
     False -> 
       case x > 10 {
          True -> ...
          False -> 
            case x <= 10 {
               True -> ...
               False -> ...
            }
       }
   }

6 comments

ngruhn

WJW 1 month ago

There are (some) guards available though? You could rewrite your example as:

    case x {
      n if x < 0 -> ...
      n if x > 10 -> ...
      n if x <= 10 -> ...
    }

Guards are a bit limited in that they cannot contain function calls, but that's a problem of the BEAM and not something Gleam could control.

ngruhn 1 month ago
Ah right, I remember now.
> Guards are a bit limited in that they cannot contain function calls,
I feel like that's not a small sacrifice.
> but that's a problem of the BEAM and not something Gleam could control.
Could Gleam desugar to a case expression like I wrote above?
- zelphirkalt 1 month ago
  
  Guards also eliminate checking for whether a pattern matching is comprehensive. Or do I remember wrong and the language does not check it at all?
tymscar 1 month ago
You most likely asked an AI for this. They always think there is an `if` keyword in case statements in Gleam. There isn't one, sadly.
EDIT: I am wrong. Apparently there are, but it's a bit of a strange thing where they can only be used as clauses in `if` statements, and without doing any calculations.
- WJW 1 month ago
  
  There is though?
  https://tour.gleam.run/flow-control/guards/

lpil 1 month ago

In Gleam we would typically write this code with `use`, which doesn’t introduce nesting.