gistfile1.hs

module Foo where

data FooArgs = FooArgs { foo :: String,
                         baz :: Integer }
               
fooer :: FooArgs -> String
fooer = undefined -- doesn't really matter what it does

-- missingArg = fooer (FooArgs { foo = "abc" })

-- legit = fooer (FooArgs { foo = "abc", baz = 12 })

*Foo> let missingArg = fooer (FooArgs { foo = "abc" })

:4:25:
Warning: Fields of FooArgs' not initialised: baz In the first argument offooer', namely (FooArgs {foo = "abc"})' In the expression: fooer (FooArgs {foo = "abc"}) In an equation formissingArg':
missingArg = fooer (FooArgs {foo = "abc"})
*Foo> let legit = fooer (FooArgs { foo = "abc", baz = 12 })