DA.Record

Reference documentation for Daml module DA.Record.

DA.Record

Exports the record machinery necessary to allow one to annotate

code that is polymorphic in the underlying record type.

Module Snapshot

Lifecycle

Stable.

Notices

Status: active Introduced in: 3.4.9 Removed in: - Warnings: 0 Deprecations: 0 Deprecated since: -

Data Types

type HasField x r a

= (GetField x r a, SetField x r a)

HasField is a class synonym for GetField and SetField, which respectively give you getter and setter functions for each record field automatically.

In the vast majority of use-cases, plain Record syntax should be preferred:

daml> let a = MyRecord 1 "hello"
daml> a.foo
1
daml> a.bar
"hello"
daml> a { bar = "bye" }
MyRecord {foo = 1, bar = "bye"}
daml> a with foo = 3
MyRecord {foo = 3, bar = "hello"}
daml>

For more on Record syntax, see https://docs.digitalasset.com/build/3.4/reference/daml/stdlib/DA-Record.html.

GetField x r a and SetField x r a are typeclasses taking three parameters. The first parameter x is the field name, the second parameter r is the record type, and the last parameter a is the type of the field in this record. For example, if we define a type:

data MyRecord = MyRecord with
    foo : Int
    bar : Text

Then we get, for free, the following GetField and SetField instances:

GetField "foo" MyRecord Int
SetField "foo" MyRecord Int
GetField "bar" MyRecord Text
SetField "bar" MyRecord Text

If we want to get a value, we can use the getField method of class GetField:

getFoo : MyRecord -> Int
getFoo r = getField @"foo" r

getBar : MyRecord -> Text
getBar r = getField @"bar" r

Note that this uses the “type application” syntax ( f @t ) to specify the field name.

Likewise, if we want to set the value in the field, we can use the setField method of class SetField:

setFoo : Int -> MyRecord -> MyRecord
setFoo a r = setField @"foo" a r

setBar : Text -> MyRecord -> MyRecord
setBar a r = setField @"bar" a r

Typeclasses

class GetField x r a

GetField x r a provides the getter part of HasField

Methods:

• getField : r -> a

Instances:

• instance GetField _1 (a, b) a
• instance GetField _1 (a, b, c) a
• instance GetField _1 (a, b, c, d) a
• instance GetField _1 (a, b, c, d, e) a
• instance GetField _2 (a, b) b
• instance GetField _2 (a, b, c) b
• instance GetField _2 (a, b, c, d) b
• instance GetField _2 (a, b, c, d, e) b
• instance GetField _3 (a, b, c) c
• instance GetField _3 (a, b, c, d) c
• instance GetField _3 (a, b, c, d, e) c
• instance GetField _4 (a, b, c, d) d
• instance GetField _4 (a, b, c, d, e) d
• instance GetField _5 (a, b, c, d, e) e
• instance GetField appEndo (Endo a) (a -> a)
• instance GetField category FailureStatus FailureCategory
• instance GetField errorId FailureStatus Text
• instance GetField getAll All Bool
• instance GetField getAny Any Bool
• instance GetField getAnyView AnyView Any
• instance GetField getAnyViewInterfaceTypeRep AnyView InterfaceTypeRep
• instance GetField hd (NonEmpty a) a
• instance GetField map (Set k) (Map k ())
• instance GetField message FailureStatus Text
• instance GetField message ArithmeticError Text
• instance GetField message AssertionFailed Text
• instance GetField message GeneralError Text
• instance GetField message PreconditionFailed Text
• instance GetField meta FailureStatus (TextMap Text)
• instance GetField runState (State s a) (s -> (a, s))
• instance GetField srcLocEndCol SrcLoc Int
• instance GetField srcLocEndLine SrcLoc Int
• instance GetField srcLocFile SrcLoc Text
• instance GetField srcLocModule SrcLoc Text
• instance GetField srcLocPackage SrcLoc Text
• instance GetField srcLocStartCol SrcLoc Int
• instance GetField srcLocStartLine SrcLoc Int
• instance GetField tl (NonEmpty a) [a]

class SetField x r a

SetField x r a provides the setter part of HasField

Methods:

• setField : a -> r -> r

Instances:

• instance SetField _1 (a, b) a
• instance SetField _1 (a, b, c) a
• instance SetField _1 (a, b, c, d) a
• instance SetField _1 (a, b, c, d, e) a
• instance SetField _2 (a, b) b
• instance SetField _2 (a, b, c) b
• instance SetField _2 (a, b, c, d) b
• instance SetField _2 (a, b, c, d, e) b
• instance SetField _3 (a, b, c) c
• instance SetField _3 (a, b, c, d) c
• instance SetField _3 (a, b, c, d, e) c
• instance SetField _4 (a, b, c, d) d
• instance SetField _4 (a, b, c, d, e) d
• instance SetField _5 (a, b, c, d, e) e
• instance SetField appEndo (Endo a) (a -> a)
• instance SetField category FailureStatus FailureCategory
• instance SetField errorId FailureStatus Text
• instance SetField getAll All Bool
• instance SetField getAny Any Bool
• instance SetField getAnyView AnyView Any
• instance SetField getAnyViewInterfaceTypeRep AnyView InterfaceTypeRep
• instance SetField hd (NonEmpty a) a
• instance SetField map (Set k) (Map k ())
• instance SetField message FailureStatus Text
• instance SetField message ArithmeticError Text
• instance SetField message AssertionFailed Text
• instance SetField message GeneralError Text
• instance SetField message PreconditionFailed Text
• instance SetField meta FailureStatus (TextMap Text)
• instance SetField runState (State s a) (s -> (a, s))
• instance SetField srcLocEndCol SrcLoc Int
• instance SetField srcLocEndLine SrcLoc Int
• instance SetField srcLocFile SrcLoc Text
• instance SetField srcLocModule SrcLoc Text
• instance SetField srcLocPackage SrcLoc Text
• instance SetField srcLocStartCol SrcLoc Int
• instance SetField srcLocStartLine SrcLoc Int
• instance SetField tl (NonEmpty a) [a]