Add versions of toTensor that take a type as their second argument (#…

…652)

These are convenience functions which are equivalent to calling the regular `toTensor` followed by `asType`. This makes code that uses this relatively common idiom less verbose.

src/arraymancer/laser/tensor/initialization.nim

@@ -258,6 +258,24 @@ proc toTensor*[T](a: openArray[T]): auto =
   let data = toSeq(flatIter(a))
   result = toTensor(data, shape)
 
+proc toTensor*[T; U](a: openArray[T], typ: typedesc[U]): Tensor[U] {.inline.} =
+  ## Convert an openArray into a Tensor of type `typ`
+  ##
+  ## This is a convenience function which given an input `a` is equivalent to
+  ## calling `a.toTensor().asType(typ)`. If `typ` is the same type of the
+  ## elements of `a` then it is the same as `a.toTensor()` (i.e. there is no
+  ## overhead).
+  ##
+  ## Inputs:
+  ##      - An array or a seq (can be nested)
+  ##      - The target type of the result Tensor
+  ## Result:
+  ##      - A Tensor of the selected type and the same shape as the input
+  when T is U:
+    toTensor(a)
+  else:
+    toTensor(a).asType(typ)
+
 proc toTensor*[T](a: SomeSet[T]): auto =
   ## Convert a HashSet or an OrderedSet into a Tensor
   ##
@@ -270,6 +288,24 @@ proc toTensor*[T](a: SomeSet[T]): auto =
   let data = toSeq(a)
   result = toTensor(data, shape)
 
+proc toTensor*[T; U](a: SomeSet[T], typ: typedesc[U]): Tensor[U] {.inline.} =
+  ## Convert a HashSet or an OrderedSet into a Tensor of type `typ`
+  ##
+  ## This is a convenience function which given an input `a` is equivalent to
+  ## calling `a.toTensor().asType(typ)`. If `typ` is the same type of the
+  ## elements of `a` then it is the same as `a.toTensor()` (i.e. there is no
+  ## overhead).
+  ##
+  ## Inputs:
+  ##      - An HashSet or an OrderedSet
+  ##      - The target type of the result Tensor
+  ## Result:
+  ##      - A Tensor of the selected type
+  when T is U:
+    toTensor(a)
+  else:
+    toTensor(a).asType(typ)
+
 proc fromBuffer*[T](rawBuffer: ptr UncheckedArray[T], shape: varargs[int], layout: static OrderType): Tensor[T] =
   ## Creates a `Tensor[T]` from a raw buffer, cast as `ptr UncheckedArray[T]`. The
   ## size derived from the given shape must match the size of the buffer!

tests/tensor/test_init.nim

@@ -85,6 +85,10 @@ proc main() =
       else:
         echo "Bound-checking is disabled or OpenMP is used. The incorrect seq shape test has been skipped."
 
+      # Call `toTensor` with a target type
+      let t5 = [1, -3, 4].toTensor(Complex64)
+      check t5 == [complex(1.0), complex(-3.0), complex(4.0)].toTensor
+
     test "Check that Tensor shape is in row-by-column order":
       let s = @[@[1,2,3],@[3,2,1]]
       let t = s.toTensor()