Gleam: Allow parenthesis around expressions

[rawburt]

pub fn convert(temp) {
  case temp {
  | {"c", t} -> ((t*(9/5))+32)
  | {"f", t} -> ((t-32)*5/9)
  }
}

I've tried various forms of this and it seems arbitrary parenthesis are not allowed. Is this expected behavior?

[lpil]

Parenthesis would be nice but they would make the syntax ambiguous. Take this program:

fn run() {
  name
  (1 * 2)
}

Is it a discarded variable followed by a grouped expression or is it calling the function name with the argument 1 * 2? Whitespace is syntactically irreverent in Gleam so we cannot tell.

If you wish to group expression to change precedence you can use begin end, which sadly is somewhat unwieldy.

[rawburt]

@lpil How would you approach writing ((t*(9/5))+32)? If you do t * 9 / 5 + 32 then t*9 would happen first considering order of operations, no?

[lpil]

That expression evalutes to the same value if all the parens are removed, but if you want to change the precedence either use begin end or extract variables.

let x = 9 / 5
t * x + 32

t * begin 9 / 5 end + 32

[lpil]

I'm going to close this as there's no work to be done. If you have an idea for nicer syntax here please open a new issue. Thank you :)

[OvermindDL1]

Is it a discarded variable followed by a grouped expression or is it calling the function name with the argument 1 * 2? Whitespace is syntactically irreverent in Gleam so we cannot tell.

Well in OCaml it would be the function name called with the single argument of 1 * 2. ^.^

[lpil]

OCaml is certainly more elegant here! :)

On Thu, 13 Jun 2019, 17:41 OvermindDL1, [e-mail] wrote:

Is it a discarded variable followed by a grouped expression or is it
calling the function name with the argument 1 * 2? Whitespace is
syntactically irreverent in Gleam so we cannot tell.

Well in OCaml it would be the function name called with the single
argument of 1 * 2. ^.^

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[edman]

I get an error with begin .. end. Is it no longer supported?

error: Unknown variable
   ┌─ 
   │
29 │     7 * begin 9 / 5 end + 32
   │         ^^^^^ did you mean `Seattle`?

The name `begin` is not in scope here.

[lpil]

Hello! It use braces these days

7 * { 2 + 3 }