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Diffstat (limited to 'Generics')
| -rw-r--r-- | Generics/README.md | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/Generics/README.md b/Generics/README.md index a6ffbee..b8e44e6 100644 --- a/Generics/README.md +++ b/Generics/README.md @@ -8,33 +8,53 @@ Warning: This is an example about an undocumented feature of Limbo. All assertio ### generics.b:17,21 +This is a polymorphic type. The type `T` is the generic type which will match whatever type is provided with a given instantiation/declaration of the `Rd` adt type. +Note the method declaration format for the adt to operate on the variable instance the method is called upon. ### generics.b:23,32 +This is an adt with pick tags. An adt with pick tags is roughly equivalent to an interpretation of unions from C. +If the variable type is instantiated with a `.Type` clause then the pick within the adt will be called looking for a match for `Type =>`. If the case is matched, then the contents of the case segment will be included with the related instantiation of the aforementioned variable. + +Note that there are two different calling formats for pick, in an adt, and in a function. ### generics.b:34,44 +This is a polymorphic adt which also possesses pick tags. +Note that the member `w` is of type `T`, implying it is matched to the type with which the adt is intantiated. Additionally, pick tag types are separate from generic `T` types, as is shown later. ### generics.b:46,50 - +This is an adt with a type definition declared which acts as a shortcut to a reference to an instance of said adt. ### generics.b:56,63 - +This section instantiates an `Rd` instance with `T` declared to be of type `ref Iobuf` for the variable `rd`. The `ws()` function reads from the provided `ref Iobuf` until a non-whitespace character is processed. `.ws()` is defined at: generics.b:103,109 +Note that instances of polymorphic types are always prefixed with `ref`. + ### generics.b:65,69 +This section instantiates two variable instances of the `Num` type using `Int` and `String` as the pick type, respectively. The `stringify()` method is called on both, fulfilling the `string` output type for printing despite the differing pick tag declarations. +In this case, `stringify()` uses the pick switch to determine which variable to access and what string to output. + +Note that instances of types with pick tags are always prefixed with `ref`. ### generics.b:71,83 +This section uses both pick tags and polymorphic types at once. + +The list `words` is a list of references to `Word` adt's with `Int` as its `T` type and `String` as its pick tag. +The variable `sword` instantiates a reference to a `Word` adt with `Int` as its `T` type and `String` as its pick tag. + +The `ismember()` function applies an interface-like check as a `for { T => }` on its arguments looking for a fulfilling `eq()` function to determine whether two types are equivalent. `ismember()` is defined at: generics.b:132,144 @@ -42,13 +62,15 @@ Warning: This is an example about an undocumented feature of Limbo. All assertio ### generics.b:85,87 +This section takes in a list and reverses said list. +Note that the `rev()` function doesn't care what type the list is a list of, it uses the type provided within its arguments. `rev()` is defined at: generics.b:154,161 ### generics.b:89,98 - +The `pair()` function allows two separate types `T`, indicated as `T1` and `T2`. Both types can be used and are matched based on the order of types in its arguments. `pair()` is defined at: generics.b:146,152 @@ -67,6 +89,7 @@ Warning: This is an example about an undocumented feature of Limbo. All assertio ## Exercises +- Try changing the pick tag for one of the instances of `Num`, how does `stringify()` behave? - Can you find a way to make the `eq()` function do a deep comparison of `Int`'s? - Try removing the `.String` from the `words` definition, what happens? - Try removing `ref anywhere, see what happens. |