This directory contains an evolving selection of examples of Nickel programs.

Please follow the main repository's README instructions to have a working nickel executable. You can then either use the command line or launch an interactive session. Play with the values to see contracts failing when fed with invalid data!

• Base values: some examples just return numbers, strings or booleans. You can run them directly:

  $ nickel eval fibonacci.ncl
  55

• Configurations: some examples return records representing configuration. You can run them directly as well, or use the export subcommand to see the result serialized as JSON, which might be more readable:

  $ nickel export merge-main.ncl
  {
    "firewall": {
    ...
  }

  Alternatively, you can query individual elements of a configuration, showing documentation and other metadata:

  $ nickel query --field kind record-contract.ncl
    • contract: [|'ReplicationController, 'ReplicaSet, 'Pod|]
    • documentation: The kind of the element being configured.

First start the REPL:

$ nickel repl
nickel>

• Just import a file directly to evaluate it:

  nickel> import "fibonacci.ncl"
  55
  
  nickel>
  

• Use std.serialize to have the same behavior as the export subcommand and print the result as JSON:

  nickel> builtin.serialize 'Json (import "merge-main.ncl")
  "{
      \"firewall\": {
      ...
  }"
  
  nickel>
  

• Use :query to retrieve information and documentation about a field:

  nickel> let config = import "record-contract.ncl"
  nickel> :query config.kind
  • contract: [| 'ReplicationController, 'ReplicaSet, 'Pod |]
  • documentation: The kind of the element being configured.
  
  nickel>