Structs in PureScript

Our structs.ps example demonstrates how to work with records in the PureScript programming language.

PureScript’s Record types are type-safe collections of fields, which are useful for grouping data together to form records. Here’s the full source code in PureScript:

module Main where

import Prelude
import Effect.Console (log)
import Effect (Effect)

-- This `Person` type has `name` and `age` fields.
type Person = 
  { name :: String
  , age  :: Int
  }

-- `newPerson` constructs a new person record with the given name.
newPerson :: String -> Person
newPerson name =
  { name: name
  , age: 42
  }

main :: Effect Unit
main = do
  -- This syntax creates a new record.
  log $ show { name: "Bob", age: 20 }

  -- You can name the fields when initializing a record.
  log $ show { name: "Alice", age: 30 }

  -- Omitted fields will result in type errors, so all fields must be provided.
  log $ show { name: "Fred", age: 0 }

  -- Here's how to create a pointer to a record. This isn't directly required in PureScript.
  let ann = { name: "Ann", age: 40 }
  log $ show ann

  -- It's idiomatic to encapsulate new record creation in constructor functions.
  log $ show (newPerson "Jon")

  -- Access record fields with a dot.
  let sean = { name: "Sean", age: 50 }
  log $ show sean.name

  -- You can also modify records using record updates.
  let updatedAge = sean { age = 51 }
  log $ show updatedAge.age

  -- If a record type is only used for a single value, we don’t
  -- have to name it. Here’s an anonymous record.
  let dog = { name: "Rex", isGood: true }
  log $ show dog

When running this PureScript program, you will see the following output:

$ spago run
Record { name: "Bob", age: 20 }
Record { name: "Alice", age: 30 }
Record { name: "Fred", age: 0 }
Record { name: "Ann", age: 40 }
Record { name: "Jon", age: 42 }
"Sean"
50
51
Record { name: "Rex", isGood: true }

Now that you can work with records in PureScript, let’s learn more about the language.

Strings and Runes in PureScript

Methods in PureScript

Learn X By Example

Title here

Structs in PureScript