add sorting example

Author: nshaffer

FortranCon2021-stdlib/examples/Makefile

@@ -2,15 +2,19 @@ FC = gfortran
 STDLIB_CFLAGS = $(shell pkg-config --cflags fortran_stdlib)
 STDLIB_LIBS = $(shell pkg-config --libs fortran_stdlib)
 
-all: ex_bitsets ex_logger
+all: ex_bitsets ex_logger ex_sorting
 
 ex_bitsets: ex_bitsets.f90
 	$(FC) $(STDLIB_CFLAGS) $^ -o $@ $(STDLIB_LIBS)
 
 ex_logger: ex_logger.f90
 	$(FC) $(STDLIB_CFLAGS) $^ -o $@ $(STDLIB_LIBS)
 
+ex_sorting: ex_sorting.f90
+	$(FC) $(STDLIB_CFLAGS) $^ -o $@ $(STDLIB_LIBS)
+
 clean:
 	$(RM) ex_bitsets
 	$(RM) ex_logger
+	$(RM) ex_sorting
 

FortranCon2021-stdlib/stdlib-talk.pdf

@@ -184,6 +184,38 @@
 \end{frame}
 
 
+\begin{frame}[fragile]
+  \frametitle{Demo: stdlib\_sorting}
+  \begin{block}{ex\_sorting.f90}
+    \small
+\begin{verbatim}
+use stdlib_sorting, only: sort_index
+use stdlib_kinds, only: int64
+implicit none
+
+integer :: digits(6) = [3,1,4,1,5,9]
+character :: chars(6) = ['a','b','c','d','e','f']
+integer(int64) :: index(6)
+call sort_index(digits, index)
+print '(6i1)', digits       ! 113459
+print '(6i1)', index        ! 241356
+print '(6a1)', chars(index) ! bdacef
+end
+\end{verbatim}
+  \end{block}
+
+  \note{
+    And finally, we'll have a brief look at the new sorting module.
+    Currently, there are three sorting subroutines.
+    Two, called ``sort'' and ``ord_sort'' are for basic in-place sorting, with different tradeoffs.
+    The third, ``sort_index'', is what some other languages call ``argsort''.
+    In addition to performing a sort, it returns an array of the indices  that put the original array in sorted order.
+    You can then use this as a vector subscript to permute other arrays in the same way.
+    All three sorting sorting routines can also sort in descending order and can take a user-supplied workspace array to allocating internal workspace.
+  }
+\end{frame}
+
+
 \begin{frame}
   \frametitle{New contributors have been key to stdlib's growth}