rename default -> optval

Author: nshaffer

src/CMakeLists.txt

@@ -2,7 +2,7 @@ set(SRC
     stdlib_experimental_ascii.f90
     stdlib_experimental_io.f90
     stdlib_experimental_error.f90
-    stdlib_experimental_default.f90
+    stdlib_experimental_optval.f90
 )
 
 add_library(fortran_stdlib ${SRC})

src/Makefile.manual

@@ -1,7 +1,7 @@
 SRC = stdlib_experimental_ascii.f90 \
       stdlib_experimental_error.f90 \
       stdlib_experimental_io.f90 \
-      stdlib_experimental_default.f90 \
+      stdlib_experimental_optval.f90 \
       f18estop.f90
 
 LIB = libstdlib.a

src/stdlib_experimental_default.f90

@@ -0,0 +1,153 @@
+module stdlib_experimental_optval
+  !!
+  !! Provides a generic function `optval`, which can be used to
+  !! conveniently implement fallback values for optional arguments
+  !! to subprograms. If `x` is an `optional` parameter of a
+  !! subprogram, then the expression `optval(x, default)` inside that
+  !! subprogram evaluates to `x` if it is present, otherwise `default`.
+  !!
+  !! It is an error to call `optval` with a single actual argument.
+  !!
+  use iso_fortran_env, only: sp => real32, dp => real64, qp => real128, int8, int16, int32, int64
+  implicit none
+
+
+  private
+  public :: optval
+
+
+  interface optval
+     module procedure optval_sp
+     module procedure optval_dp
+     module procedure optval_qp
+     module procedure optval_int8
+     module procedure optval_int16
+     module procedure optval_int32
+     module procedure optval_int64
+     module procedure optval_logical
+     module procedure optval_character
+     ! TODO: complex kinds
+     ! TODO: differentiate ascii & ucs char kinds
+  end interface optval
+
+
+contains
+
+
+  function optval_sp(x, default) result(y)
+    real(sp), intent(in), optional :: x
+    real(sp), intent(in) :: default
+    real(sp) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_sp
+
+
+  function optval_dp(x, default) result(y)
+    real(dp), intent(in), optional :: x
+    real(dp), intent(in) :: default
+    real(dp) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_dp
+
+
+  function optval_qp(x, default) result(y)
+    real(qp), intent(in), optional :: x
+    real(qp), intent(in) :: default
+    real(qp) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_qp
+
+
+  function optval_int8(x, default) result(y)
+    integer(int8), intent(in), optional :: x
+    integer(int8), intent(in) :: default
+    integer(int8) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_int8
+
+
+  function optval_int16(x, default) result(y)
+    integer(int16), intent(in), optional :: x
+    integer(int16), intent(in) :: default
+    integer(int16) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_int16
+
+
+  function optval_int32(x, default) result(y)
+    integer(int32), intent(in), optional :: x
+    integer(int32), intent(in) :: default
+    integer(int32) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_int32
+
+
+  function optval_int64(x, default) result(y)
+    integer(int64), intent(in), optional :: x
+    integer(int64), intent(in) :: default
+    integer(int64) :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_int64
+
+
+  function optval_logical(x, default) result(y)
+    logical, intent(in), optional :: x
+    logical, intent(in) :: default
+    logical :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_logical
+
+
+  function optval_character(x, default) result(y)
+    character(len=*), intent(in), optional :: x
+    character(len=*), intent(in) :: default
+    character(len=:), allocatable :: y
+
+    if (present(x)) then
+       y = x
+    else
+       y = default
+    end if
+  end function optval_character
+
+end module stdlib_experimental_optval