generic.md
In S7: An Object Oriented System Meant to Become a Successor to S3 and S4

new_generic checks its inputs

Code
  new_generic(1)
Condition
  Error:
  ! `name` must be a single string
Code
  new_generic("")
Condition
  Error:
  ! `name` must not be "" or NA
Code
  new_generic("foo", 1)
Condition
  Error:
  ! `dispatch_args` must be a character vector
Code
  new_generic("foo", "x", function(x) { })
Condition
  Error:
  ! `fun` must contain a call to `S7_dispatch()`

check_dispatch_args() produces informative errors

Code
  check_dispatch_args(1)
Condition
  Error:
  ! `dispatch_args` must be a character vector
Code
  check_dispatch_args(character())
Condition
  Error:
  ! `dispatch_args` must have at least one component
Code
  check_dispatch_args("")
Condition
  Error in `check_dispatch_args()`:
  ! `dispatch_args` must not be missing or the empty string
Code
  check_dispatch_args(NA_character_)
Condition
  Error in `check_dispatch_args()`:
  ! `dispatch_args` must not be missing or the empty string
Code
  check_dispatch_args(c("x", "x"))
Condition
  Error:
  ! `dispatch_args` must be unique
Code
  check_dispatch_args("...")
Condition
  Error:
  ! Can't dispatch on `...`
Code
  check_dispatch_args("y", function(x, ..., y) { })
Condition
  Error:
  ! `dispatch_args` must be a prefix of the generic arguments

S7_generic printing

Code
  foo1
Output
  <S7_generic> foo1(x, ...) with 2 methods:
  1: method(foo1, class_character)
  2: method(foo1, text)
Code
  foo3
Output
  <S7_generic> foo3(x, y, z, ...) with 3 methods:
  1: method(foo3, list(class_character, class_integer, class_character))
  2: method(foo3, list(class_character, class_integer, class_logical))
  3: method(foo3, list(class_character, text, class_character))

S7_generic printing with long / many arguments

Code
  foo
Output
  <S7_generic> foo(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z, ...) with 0 methods:

check_generic produces informative errors

Code
  check_generic("x")
Condition
  Error:
  ! `fun` must be a function
Code
  check_generic(function() { })
Condition
  Error:
  ! `fun` must contain a call to `S7_dispatch()`