This module defines compile-time reflection procs for working with types.

Unstable API.


proc name(t: typedesc): string {...}{.magic: "TypeTrait".}

Returns the name of the given type.

Alias for system.`$`(t) since Nim v0.20.

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proc arity(t: typedesc): int {...}{.magic: "TypeTrait".}
Returns the arity of the given type. This is the number of "type" components or the number of generic parameters a given type t has.


assert arity(seq[string]) == 1
assert arity(array[3, int]) == 2
assert arity((int, int, float, string)) == 4
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proc genericHead(t: typedesc): typedesc {...}{.magic: "TypeTrait".}

Accepts an instantiated generic type and returns its uninstantiated form.

For example:

  • seq[int].genericHead will be just seq
  • seq[int].genericHead[float] will be seq[float]

A compile-time error will be produced if the supplied type is not generic.

See also:


  Functor[A] = concept f
    type MatchedGenericType = genericHead(f.type)
      # `f` will be a value of a type such as `Option[T]`
      # `MatchedGenericType` will become the `Option` type
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proc stripGenericParams(t: typedesc): typedesc {...}{.magic: "TypeTrait".}
This trait is similar to genericHead, but instead of producing error for non-generic types, it will just return them unmodified.   Source Edit
proc supportsCopyMem(t: typedesc): bool {...}{.magic: "TypeTrait".}

This trait returns true iff the type t is safe to use for copyMem.

Other languages name a type like these blob.

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proc isNamedTuple(T: typedesc): bool
Return true for named tuples, false for any other type.   Source Edit


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