Basic Questions

Questions
1

I created sample app, create-daml-app mentioned in the documentation.
Added one sample file:
create-daml-app/daml/Refer.daml with below content:

module Refer where

I have few questions:

  1. Why we add module where
  2. Can’t I run any sample script directly… do I need to have UI app in place.
  3. Can we have daml app which is has no UI, simaply a backend app with a simple script.
  4. Do I need a create a project just to execute basic script say which concatenates two lists
  5. Daml supports React by default-- Any support for Angular
  6. Is there support for third party API calls… by using rest client or so…
  7. Is it possible to declare global variables and use them anywhere in a script.
  8. in the code below why script keyword is missing before do
    cash_balance_test = do
    accountant ← allocateParty “Bob”

How above code different from below one:

cash_balance_test = script do
accountant ← allocateParty “Bob”
owner ← allocateParty “Alice”
owner ← allocateParty “Alice”

2

Hi @kanika_kapoor,

In general, it is best to open separate threads for separate questions. Asking so many questions at once can lead to very fragmented conversations, making the thread hard to follow.

Here’s my attempts at answering your questions:

  1. That’s just syntax we inherit from Haskell. Most languages have some equivalent module / package / namespace declaration at the top of their files.
  2. You do not need a UI app to run a script, especially a Daml Script.
  3. Yes. See the quickstart-java template for a terse example.
  4. In the Daml world, “script” is usually taken to mean “Daml Script”, which does indeed require a project: to run a Daml Script, you need to have a DAR flle, and to get a DAR file you need a project. Alternatively, you can run daml repl and play with the language one line at a time, with no project required.
  5. No, we do not have official support for any other frontend framework than React. Note that our JavaScript support is offered in three separate libraries: @daml/types, @daml/ledger, and @daml/react. The last one is a thin compatibility layer between React and @daml/ledger; @daml/ledger does not know anything about React (or the browser) and can be used in other environments (Angular, NodeJS, etc.). I don’t know much about Angular myself but if you do, it should be possible to just use @daml/ledger in your Angular application.
  6. The Daml system itself cannot make external API calls. External systems can interact with a Daml Ledger either directly through gRPC or through the JSON API Service (which runs as a separate component and, itself, connects to the gRPC endpoint). If you need to bridge a Daml Ledger to an external API, you’ll have to build your own application that talks to both.
  7. It is not possible to declare variables in Daml: the language is pure. You can bind symbols to immutable values, and you can shadow these bindings for a llimited scope. You can bind a value globally, but it’s still not going to be variable.
  8. The do notation is very flexible and can mean any number of things. The compiler needs that script call to know what to do with the do block. Think of the do block as being an argument to the script function.
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