apply -- apply `f.call` to the value stored in this choice

This can be used to perform operation on values of arbitray choice types.

Example:


which prints

create a string from this choice.

This will use the value stored stored in this choice and create its String
representation using `prefix $` and return that without any additional
information.

create a detailed string from this choice.

This will createa string of the form `type.tag(T,v)` consisting of
the string representations of


So, e.g., `(id (option String) "hi").as_string` will result in
`"option String.0(String,hi)"`

combine -- if `choice.this` and `other` have the same ordinal number, combine
the value stored in this `ta` and in other `ov` using `f.call va vb`.
Otherwise, return `e`.

This can be used to combine values of arbitrary choice types.

dynamic_apply -- apply `f.call` to `Any.this`'s dynamic type and value

This can be used to perform operation on values depending on their dynamic
type.

Here is an example that takes a `Sequence Any` that may contain boxed values
of types `i32` and `f64`. We can now write a feature `get_f64` that extracts
these values converted to `f64` and build a function `sum` that sums them up
as follows:

Get the dynamic type of this instance. For value instances `x`, this is
equal to `type_of x`, but for `x` with a `ref` type `x.dynamic_type` gives
the actual runtime type, while `type_of x` results in the static
compile-time type.

There is no dynamic type of a type instance since this would result in an
endless hierarchy of types. So for Type values, dynamic_type is redefined
to just return Type.type.

Ordinal number corresponding to the index in this choice's open type
parameters of the type of the value stored in this choice.

Note that this is defined even for choices of ambiguous types like
`option nil`: Even though this type may only contain `nil` it can
still be distinguished:


is `0` while


is `1`.

convenience prefix operator to create a string from a value.

This permits usage of `$` as a prefix operator in a similar way both
inside and outside of constant strings: $x and "$x" will produce the
same string.

the native value used for this clock

string representation of this type to be used for debugging.

result has the form "<name>", but this might change in the future

There is no dynamic type of a type instance since this would result in an
endless hierarchy of types, so dynamic_type is redefined to just return
Type.type here.

Note: Typechecking is undecidable when 'type' is a type, Mark B. Reinhold, 1989
see: https://dspace.mit.edu/bitstream/handle/1721.1/149366/MIT-LCS-TR-458.pdf?sequence=6

equality of two choices `a` and `b` is defined only if all element types
of the choice are equatable. The choices are equal if they have the same
ordinal number and the contained values are equal.

This will result in a compile time panic in case any element type is not
equatable.

create hash code for this instance

This should satisfy the following condition:

(T.equality a b) : (T.hash_code a = T.hash_code b)

Is this type assignable to a type parameter with constraint `T`?

The result of this is a compile-time constant that can be used to specialize
code for a particular type.


it is most useful in conjunction with preconditions or `if` statements as in


or

A total order between two choices `a` and `b` is defined only if all element types
of the choice are orderable.
their first elements. If the first `i` element pairs are equal, the order is defined by
the `i+1`th element pair.

This will result in a compile time panic in case any element type is not
orderable.

name of this type, including type parameters, e.g. 'option (list i32)'.

convenience prefix operator to create a string from a value.

This permits usage of `$` as a prefix operator in a similar way both
inside and outside of constant strings: $x and "$x" will produce the
same string.

NYI: Redefinition allows the type feature to be distinguished from its normal counterpart, see #3913

Get a type as a value.

This is a feature with the effect equivalent to Fuzion's `expr.type` call tail.
It is recommended to use `expr.type` and not `expr.type_value`.

`type_value` is here to show how this can be implemented and to illustrate the
difference to `dynamic_type`.

equals -- feature that compares two values using the equality relation
defined in their type

hash of a value

infix = -- infix operation as shorthand for 'equals'

does this come strictly before other?

infix <= -- infix operation as shorthand for 'lteq'

three-way comparison between this and other.

result is < 0 if this < other
result is > 0 if this > other
result is = 0 if this = other

infix = -- infix operation as shorthand for 'equals'

does this come strictly after other?

does this come after other?

is `a` contained in `Set` `s`?

This should usually be called using type inference as in

is `a` not contained in `Set` `s`?

This should usually be called using type inference as in

infix ≤ -- infix operation as shorthand for 'lteq'

does this come after other?

three-way comparison between this and other.

result is < 0 if this < other
result is > 0 if this > other
result is = 0 if this = other

lteq -- feature that compares two values using the lteq relation
defined in their type

maximum of two values

memoize `f`.
wraps f so that f will only be called once for every unique input.

The term "memoization" was coined by Donald Michie in 1968 and
is derived from the Latin word "memorandum" ("to be remembered"),
usually truncated as "memo" in American English, and thus carries
the meaning of "turning a function into something to be remembered".
https://en.wikipedia.org/wiki/Memoization

example:

minimum of two values