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+/*
+BioNix is a thin wrapper over Nix: there is not much functionality
+required for pipelining that is not already present in the base build
+engine. As such, the focus is on providing an interface that is
+convenient for specifying common bioinformatics workflows. To this end,
+BioNix provides a library of tools to help simplify the specification of
+common bioinformatics pipelines, with a notable focus on genomics tools.
+You can see the available tools at
+https://github.com/PapenfussLab/bionix/tree/master/tools.
+
+This exercise aims to demonstrate how to both use a tool available in
+BioNix on some input data and how to chain them together. We will do a
+simple alignment with BWA on some simulated reads from a bacterial
+genome. The BWA tool is provided by
+https://github.com/PapenfussLab/bionix/blob/master/tools/bwa.nix and as
+you can see there are alignment functions for alignment with BWA/BWA2,
+as well as corresponding index functions for indexing a reference
+genome.  Don't worry about indexing, this will be handled automatically,
+you only have to declare you want an alignment and what genome and the
+index will be generated if needed.
+
+Exercise:
+
+1. Sample data along with a reference will be fetched from github. As
+before, hashes of the content must be known. Fill in the hashes to fully
+specify the inputs.
+
+2. With the hashes in place, the expression should evaluate and BWA
+should run.  Try swapping BWA out with some of the other available
+aligners in BioNix (e.g., bowtie, hisat2, minimap2, whisper).
+
+3. Aligners produce *unsorted* output, but co-ordinate sorted alignments
+are usually desired as they are indexable by position. Pass the aligned
+output to the samtools sort function to sort the alignments into co-
+ordinate order.
+*/
+{bionix}:
+with bionix; let
+  input = {
+    input1 = fetchFastQ {
+      url = "https://raw.githubusercontent.com/PapenfussLab/bionix/bac9248a5e08e8afdf5485a6e27cfe72e1ca5090/examples/sample1-1.fq";
+    };
+    input2 = fetchFastQ {
+      url = "https://raw.githubusercontent.com/PapenfussLab/bionix/bac9248a5e08e8afdf5485a6e27cfe72e1ca5090/examples/sample1-2.fq";
+    };
+  };
+
+  ref = fetchFastA {
+    url = "https://raw.githubusercontent.com/PapenfussLab/bionix/bac9248a5e08e8afdf5485a6e27cfe72e1ca5090/examples/ref.fa";
+  };
+in
+  bwa.align {} input