modify optional argument; move to the top use statements in stdlib_math_meshgrid.fypp

Author: igirault

doc/specs/stdlib_math.md

@@ -602,8 +602,8 @@ Shall be arrays of type `real` or `integer` of adequate shape:
 These argument are `intent(out)`.
 
 `indexing`: the selected indexing.
-Shall be a `character(len=2)` equal to `"xy"` for Cartesian indexing (default), or `"ij"` for matrix indexing.
-This argument is `intent(in)` and `optional`, and is equal to `"xy"` by default.
+Shall be an `integer` equal to `stdlib_meshgrid_xy` for Cartesian indexing (default), or `stdlib_meshgrid_ij` for matrix indexing. `stdlib_meshgrid_xy` and `stdlib_meshgrid_ij` are public constants defined in the module.
+This argument is `intent(in)` and `optional`, and is equal to `stdlib_meshgrid_xy` by default.
 
 #### Example
 

example/math/example_meshgrid.f90

@@ -1,6 +1,6 @@
 program example_meshgrid
 
-    use stdlib_math, only: meshgrid, linspace
+    use stdlib_math, only: meshgrid, linspace, stdlib_meshgrid_ij
     use stdlib_kinds, only: sp
 
     implicit none
@@ -19,7 +19,7 @@ program example_meshgrid
     print *, "ym_cart = "
     call print_2d_array(ym_cart)
 
-    call meshgrid(x, y, xm_mat, ym_mat, indexing="ij")
+    call meshgrid(x, y, xm_mat, ym_mat, indexing=stdlib_meshgrid_ij)
     print *, "xm_mat = "
     call print_2d_array(xm_mat)
     print *, "ym_mat = "

src/stdlib_math.fypp

@@ -14,6 +14,7 @@ module stdlib_math
     public :: EULERS_NUMBER_QP
 #:endif
     public :: DEFAULT_LINSPACE_LENGTH, DEFAULT_LOGSPACE_BASE, DEFAULT_LOGSPACE_LENGTH
+    public :: stdlib_meshgrid_ij, stdlib_meshgrid_xy
     public :: arange, arg, argd, argpi, is_close, all_close, diff, meshgrid
 
     integer, parameter :: DEFAULT_LINSPACE_LENGTH = 100
@@ -32,6 +33,9 @@ module stdlib_math
     real(kind=${k1}$), parameter :: PI_${k1}$ = acos(-1.0_${k1}$)
     #:endfor
 
+    !> Values for optional argument `indexing` of `meshgrid`
+    integer, parameter :: stdlib_meshgrid_xy = 0, stdlib_meshgrid_ij = 1
+
     interface clip
     #:for k1, t1 in IR_KINDS_TYPES
         module procedure clip_${k1}$
@@ -401,7 +405,7 @@ module stdlib_math
             ${t1}$, intent(in) :: x${i}$(:)
             ${t1}$, intent(out) :: xm${i}$ ${ranksuffix(rank)}$
             #:endfor
-            character(len=2), intent(in), optional :: indexing
+            integer, intent(in), optional :: indexing
         end subroutine ${RName}$
         #:endfor
         #:endfor

src/stdlib_math_meshgrid.fypp

@@ -17,6 +17,8 @@
 
 submodule(stdlib_math) stdlib_math_meshgrid
 
+    use stdlib_error, only: error_stop
+
 contains
 
     #:for k1, t1 in IR_KINDS_TYPES
@@ -30,15 +32,13 @@ contains
     #:endif
     #: set RName = rname("meshgrid", rank, t1, k1)
     module procedure ${RName}$
-        use stdlib_optval, only: optval
-        use stdlib_error, only: error_stop
 
         integer :: ${"".join(f"i{j}," for j in range(1, rank + 1)).removesuffix(",")}$
 
-        select case (optval(indexing, "xy"))
-        case ("xy")
+        select case (optval(indexing, stdlib_meshgrid_xy))
+        case (stdlib_meshgrid_xy)
             $:meshgrid_loop(XY_INDICES)
-        case ("ij")
+        case (stdlib_meshgrid_ij)
             $:meshgrid_loop(IJ_INDICES)
         case default
             call error_stop("ERROR (meshgrid): unexpected indexing.")

test/math/test_meshgrid.fypp

@@ -7,13 +7,13 @@
 
 #:def OPTIONAL_PART_IN_SIGNATURE(indexing)
 #:if indexing in ("xy", "ij")
-  ${f', "{indexing}"'}$
+  ${f', stdlib_meshgrid_{indexing}'}$
 #:endif
 #:enddef
 
 module test_meshgrid
     use testdrive, only : new_unittest, unittest_type, error_type, check
-    use stdlib_math, only: meshgrid
+    use stdlib_math, only: meshgrid, stdlib_meshgrid_ij, stdlib_meshgrid_xy
     use stdlib_kinds, only: int8, int16, int32, int64, sp, dp, xdp, qp
     implicit none