Update eye function.

Author: zoziha

doc/specs/stdlib_linalg.md

@@ -101,21 +101,29 @@ end program demo_diag5
 
 Experimental
 
+### Class
+
+Pure function.
+
 ### Description
 
-Construct the identity matrix
+Construct the identity matrix.
 
 ### Syntax
 
-`I = [[stdlib_linalg(module):eye(function)]](n)`
+`I = [[stdlib_linalg(module):eye(function)]](dim1 [, dim2])`
 
 ### Arguments
 
-`n`: Shall be a scalar of default type `integer`. 
+`dim1`: Shall be a scalar of default type `integer`.
+This is an `intent(in)` argument. 
+
+`dim2`: Shall be a scalar of default type `integer`.
+This is an `intent(in)` and `optional` argument. 
 
 ### Return value
 
-Returns the identity matrix, i.e. a square matrix with ones on the main diagonal and zeros elsewhere. The return value is of type `integer(int8)`.
+Returns the identity matrix, i.e. a square matrix with ones on the main diagonal and zeros elsewhere. The return value is of type `integer`.
 
 ### Example
 
@@ -124,7 +132,10 @@ program demo_eye1
     use stdlib_linalg, only: eye
     implicit none
     real :: a(3,3)
+    real :: b(3,4)
     A = eye(3)
+    A = eye(3,3)
+    B = eye(3,4)
 end program demo_eye1
 ```
 

src/stdlib_linalg.fypp

@@ -82,20 +82,28 @@ module stdlib_linalg
 
 contains
 
-    function eye(n) result(res)
-      !! version: experimental
-      !!
-      !! Constructs the identity matrix
-      !! ([Specification](../page/specs/stdlib_linalg.html#description_1))
-      integer, intent(in) :: n
-      integer(int8) :: res(n, n)
-      integer :: i
-      res = 0
-      do i = 1, n
-         res(i, i) = 1
-      end do
-    end function eye
+    !> Version: experimental
+    !>
+    !> Constructs the identity matrix.
+    !> ([Specification](../page/specs/stdlib_linalg.html#eye-construct-the-identity-matrix))
+    pure function eye(dim1, dim2) result(result)
+
+        integer, intent(in) :: dim1
+        integer, intent(in), optional :: dim2
+        integer, allocatable :: result(:, :)
+
+        integer :: dim2_
+        integer :: i
 
+        dim2_ = merge(dim2, dim1, present(dim2))
+        allocate(result(dim1, dim2_))
+        
+        result = 0
+        do i = 1, min(dim1, dim2_)
+            result(i, i) = 1
+        end do
+
+    end function eye
 
     #:for k1, t1 in RCI_KINDS_TYPES
       function trace_${t1[0]}$${k1}$(A) result(res)
@@ -108,4 +116,5 @@ contains
         end do
       end function trace_${t1[0]}$${k1}$
     #:endfor
-end module
+
+end module stdlib_linalg

src/tests/Makefile.manual

@@ -11,3 +11,4 @@ all test clean:
 	$(MAKE) -f Makefile.manual --directory=stats $@
 	$(MAKE) -f Makefile.manual --directory=string $@
 	$(MAKE) -f Makefile.manual --directory=math $@
+	$(MAKE) -f Makefile.manual --directory=linalg $@

src/tests/linalg/Makefile.manual

@@ -0,0 +1,4 @@
+PROGS_SRC = test_linalg.f90
+
+
+include ../Makefile.manual.test.mk

src/tests/linalg/test_linalg.f90

@@ -81,6 +81,13 @@ subroutine test_eye
     integer :: i
     write(*,*) "test_eye"
 
+    call check(all(eye(3,3) == diag([(1,i=1,3)])), &
+               msg="all(eye(3,3) == diag([(1,i=1,3)])) failed.",warn=warn)
+    
+    rye = eye(3,4)
+    call check(sum(rye(:,1:3) - diag([(1.0_sp,i=1,3)])) < sptol, &
+               msg="sum(rye(:,1:3) - diag([(1.0_sp,i=1,3)])) < sptol", warn=warn)
+
     call check(all(eye(5) == diag([(1,i=1,5)])), &
           msg="all(eye(5) == diag([(1,i=1,5)] failed.",warn=warn)