Module typetraits

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

Procs

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

Returns the name of the given type.

Example:

import typetraits

proc `$`*(T: typedesc): string = name(T)

template test(x): typed =
  echo "type: ", type(x), ", value: ", x

test 42
# --> type: int, value: 42
test "Foo"
# --> type: string, value: Foo
test(@['A','B'])
# --> type: seq[char], value: @[A, B]

proc `$`(t: typedesc): string

An alias for name.

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.

Examples:

assert arity(seq[string]) == 1
assert arity(array[3, int]) == 2
assert arity((int, int, float, string)) == 4

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.

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.

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.