Add sorting and error handling example

Author: sethrj

doc/examples.rst

@@ -6,7 +6,22 @@
 Examples
 ********
 
-TODO
+The following standalone codes demonstrate how Flibcpp can be used in native
+Fortran code.
+
+String conversion and sort
+==========================
+
+This example:
+
+ - Introspects the Flibcpp version;
+ - Converts a user input to an integer, validating it with useful error
+   messages;
+ - Fills an array with normally-distributed real numbers; and
+ - Sorts the array before printing the first few entries.
+
+.. literalinclude:: ../example/sort.f90
+   :linenos:
 
 .. ############################################################################
 .. end of doc/examples.rst

example/CMakeLists.txt

@@ -12,7 +12,7 @@ macro(swig_fortran_add_example name)
 endmacro()
 
 swig_fortran_add_example(sort
-  flc_algorithm)
+  flc_algorithm flc_random flc_string)
 
 ##---------------------------------------------------------------------------##
 ## end of common/CMakeLists.txt

example/sort.f90

@@ -1,29 +1,92 @@
 !-----------------------------------------------------------------------------!
 ! \file   example/sort.f90
+!
+! Copyright (c) 2019 Oak Ridge National Laboratory, UT-Battelle, LLC.
 !-----------------------------------------------------------------------------!
 
 program main
-    use ISO_FORTRAN_ENV
-    use, intrinsic :: ISO_C_BINDING
-    use flc
-    use flc_algorithm, only : sort
+  use ISO_FORTRAN_ENV
+  use, intrinsic :: ISO_C_BINDING
+  use flc
+  use flc_algorithm, only : sort
+  use flc_random, only : Engine, normal_distribution
+  implicit none
+  integer, parameter :: STDOUT = OUTPUT_UNIT
+  integer :: arr_size
+  real(c_double), dimension(:), allocatable :: x
+  real(c_double), parameter :: MEAN = 1.0d0, SIGMA = 0.5d0
+  type(Engine) :: rng
 
-    implicit none
-    integer :: n = 10000
-    real(c_double), dimension(:), allocatable :: x
+  ! Print version information
+  write(STDOUT, "(a)") "========================================"
+  write(STDOUT, "(a, a)") "Flibcpp version: ", get_flibcpp_version()
+  write(STDOUT, "(a, 2(i1,'.'), (i1), a)") "(Numeric version: ", &
+      flibcpp_version_major, flibcpp_version_minor, flibcpp_version_patch, &
+      ")"
+  write(STDOUT, "(a)") "========================================"
 
-    write(*,"(a, 2(i1,'.'), (i1))") "Flibcpp version number: ", &
-        flibcpp_version_major, flibcpp_version_minor, flibcpp_version_patch
-    write(*,*) "Flibcpp version string: ", get_flibcpp_version()
+  ! Get array size
+  arr_size = read_positive_int("array size")
+  allocate(x(arr_size))
 
-    allocate(x(n))
-    ! TODO: fill randomly
-    x = 1
-    call sort(x)
+  ! Fill randomly with normal distribution
+  rng = Engine()
+  call normal_distribution(MEAN, SIGMA, rng, x)
 
-    write(*,*) "Success!"
-end program
+  ! Sort the array
+  call sort(x)
+
+  ! Write output
+  write(STDOUT, "(a, 4(f8.3,','))") "First few elements:", x(:min(4, size(x)))
+contains
+
+! Loop until the user inputs a positive integer. Catch error conditions. 
+function read_positive_int(desc) result(result_int)
+  use flc
+  use flc_string, only : stoi
+  use ISO_FORTRAN_ENV
+  implicit none
+  character(len=*), intent(in) :: desc
+  integer, parameter :: STDOUT = OUTPUT_UNIT, STDIN = INPUT_UNIT
+  character(len=80) :: readstr
+  integer :: result_int, io_ierr
+  do
+    write(STDOUT, *) "Enter " // desc // ": "
+    read(STDIN, "(a)", iostat=io_ierr) readstr
+    if (io_ierr == IOSTAT_END) then
+      ! Error condition: ctrl-D during input
+      write(STDOUT, *) "End of line"
+      stop 0
+    endif
+
+    result_int = stoi(readstr)
+    if (ierr == 0) then
+      if (result_int <= 0) then
+        ! Error condition: non-positive value
+        write(STDOUT, *) "Invalid " // desc // ": ", result_int
+        continue
+      end if
 
+      write(STDOUT, *) "Read " // desc // "=", result_int
+      exit
+    endif
+
+    if (ierr == SWIG_OVERFLOWERROR) then
+      ! Error condition: integer doesn't fit in native integer
+      write(0,*) "Your integer is too darn big!"
+    else if (ierr == SWIG_VALUEERROR) then
+      ! Error condition: not an integer at all
+      write(0,*) "That text you entered? It wasn't an integer."
+    else
+      write(0,*) "Unknown error", ierr
+    end if
+    write(0,*) "(Detailed error message: ", get_serr(), ")"
+
+    ! Clear error flag so the next call to stoi succeeds
+    ierr = 0
+  end do
+end function
+end program
 
 !-----------------------------------------------------------------------------!
 ! end of example/sort.f90