Added stoiciometry_string function and tests +interactive rebase!

@stelmo format

change name of function

change name of function

src/base/utils/Reaction.jl

@@ -70,3 +70,23 @@ function is_mass_balanced(model::StandardModel, rxn::Reaction)
 
     return all(sum(values(atom_balances)) == 0), atom_balances
 end
+
+"""
+    stoichiometry_string(rxn_dict)
+
+Return the reaction equation as a string.
+
+# Example
+```
+julia> req = Dict("coa_c" => -1, "for_c" => 1, "accoa_c" => 1, "pyr_c" => -1);
+julia> stoichiometry_string(req)
+"coa_c + pyr_c = for_c + accoa_c"
+```
+"""
+function stoichiometry_string(req)
+    replace_one(n) = abs(n) == 1 ? "" : string(abs(n))
+    substrates =
+        join(strip.(["$(replace_one(n)) $met" for (met, n) in req if n < 0]), " + ")
+    products = join(strip.(["$(replace_one(n)) $met" for (met, n) in req if n >= 0]), " + ")
+    return substrates * " = " * products
+end

test/base/utils/reaction.jl

+@testset "Reaction utilities" begin
+    # test if reaction equation can be built back into a sensible reaction string
+    req = Dict("coa_c" => -1, "for_c" => 1, "accoa_c" => 1, "pyr_c" => -1)
+    rstr_out = stoichiometry_string(req)
+    @test occursin("coa_c", split(rstr_out, " = ")[1])
+    @test occursin("for", split(rstr_out, " = ")[2])
+end