Add Signal haddocks.

Author: dmjio

shell.nix

@@ -22,6 +22,9 @@ in
              'cabal v1-configure --enable-tests && \
                 cabal v1-build doctests && dist/build/doctests/doctests src/ArrayFire/Algorithm.hs'
       }
+      function exe () {
+         cabal run main
+      }
       function repl () {
         cabal v1-repl lib:arrayfire
       }

src/ArrayFire/BLAS.hs

@@ -41,7 +41,7 @@ import ArrayFire.Internal.Types
 --
 -- This function can be used with one sparse input. The sparse input must always be the lhs and the dense matrix must be rhs.
 --
--- The sparse array can only be of AF_STORAGE_CSR format.
+-- The sparse array can only be of 'CSR' format.
 --
 -- The returned array is always dense.
 --