[BUG] Expression built-ins should be formalized

[Ph0enixKM]

Describe the bug Right now lines built-in forces user to use it with parentheses:

let var = lines(file) // OK
let var = lines file // Error: Variable 'lines' does not exist

However this does not apply to len

let var = len(file) // OK
let var = len file // OK

What should be done?

• [ ] A more precise error message saying that expression built-ins should be used with parentheses
• [ ] Set the same constraints to other expression built-ins

[lens0021]

I found a problem with builtin statements that accept two parameters. Let's take an example of mv. Here is how we can use move command:

mv "old.txt" "new.txt"

This is all fine untill we introduce a builtin that accepts two arrays for instance:

builtin variable [1]
foo()

The statement written above could be interpreted in both ways:

// A separate variable and a singleton array
builtin variable [1]
foo()
// A subscript operator and function call that returns array
builtin variable[1] foo()

This leads me to the fact that we should require commas , to separate the arguments:

builtin variable, [1]

This way we can clearly see that it's a separate argument. What are your thoughts?

_Originally posted by @Ph0enixKM in https://discord.com/channels/1235872011603939328/1243872082308366386/1382279840098684938

I think we should fix this by unifing syntax. All builtin functions should have function syntax echo("text") mv("from", "to") etc.

_Originally posted by @KrosFire in https://discord.com/channels/1235872011603939328/1243872082308366386/1382283591492309022

yes probably simplify the language, I think that we talked about it also with @hdwalters

_Originally posted by @Mte90 in https://discord.com/channels/1235872011603939328/1243872082308366386/1382287906340732978

Right... I think that ultimately this could simplify the language Because splitting builtins into statement builtins and expression builtins is an unnecessary waste of time for a new developer to get into Amber

_Originally posted by @Ph0enixKM in https://discord.com/channels/1235872011603939328/1243872082308366386/1382290650908725248