Nickel language preview

1. Contracts and records

let bindings, annotations, and merging

horizon-dark

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

atom-one-dark

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

github-dark

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

dracula

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

nord

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

github

let Port = std.contract.from_predicate (fun p =>
  std.is_number p && p > 0 && p < 65536) in

{
  host | String = "localhost",
  port | Port = 8080,
  url = "http://%{host}:%{std.to_string port}",
}

2. Functions and enums

fun expressions and enum tags

horizon-dark

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

atom-one-dark

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

github-dark

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

dracula

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

nord

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

github

let classify = fun n =>
  if n > 0 then 'Positive
  else if n < 0 then 'Negative
  else 'Zero in

{
  result = classify 42,
  values = std.array.map (fun x => x * 2) [1, 2, 3],
}

3. Interpolation with a nested record

a %{...} interpolation containing a bare {..} record literal

horizon-dark

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

atom-one-dark

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

github-dark

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

dracula

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

nord

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

github

let user = { name = "Bob", age = 30 } in

{ greeting = "Hello, %{ {name = user.name}.name }!" }

4. Multiline strings

m%"..."% strings with a matching %-count delimiter

horizon-dark

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }

atom-one-dark

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }

github-dark

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }

dracula

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }

nord

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }

github

let template = m%"
  Use %{host} with a literal "%" sign here.
  "%
in
{ rendered = template }