Refactor Makefile and remove unnecessary blank lines

- Update Makefile targets to depend on specific source files
- Improve echo messages with consistent capitalization
- Remove extraneous blank lines in substitution method files
- Modify kernel method error handling in SimpleLinearAlgebra module

Author: yangjunjie0320

Makefile

@@ -1,20 +1,20 @@
 jl:=julia
 
-init: 
+init: src/SimpleLinearAlgebra.jl
 	$(jl) -e 'd=pwd(); @assert isdir(d);\
 	using Pkg: activate, instantiate, develop, precompile; \
 	activate(d); instantiate(); activate(joinpath(d, "examples")); \
 	develop(path=d); instantiate(); precompile();'
-	@echo "environment initialized at: $$PWD"
+	@echo "Environment initialized at: $$PWD"
 
-update:
+update: src/SimpleLinearAlgebra.jl
 	$(jl) -e 'd=pwd(); @assert isdir(d);\
 	using Pkg: activate, update, develop, precompile; \
 	activate(d); update(); activate(joinpath(d, "examples")); \
 	update(); precompile();'
-	@echo "environment updated at: $$PWD"
+	@echo "Environment updated at: $$PWD"
 
-test:
+test: test/runtests.jl
 	@echo "Running tests at: $$PWD"
 	$(jl) -e 'd=pwd(); @assert isdir(d);\
 	using Pkg: activate, test; \

src/SimpleLinearAlgebra.jl

@@ -6,7 +6,7 @@ module SimpleLinearAlgebra
     abstract type LinearSystemSolutionMixin end
 
     function kernel(prob::LinearSystemProblemMixin)
-        throw(MethodError(kernel, (prob,)))
+        MethodError(kernel, (typeof(prob),)) |> throw
     end
 
     include("forward_substitution.jl")

src/back_substitution.jl

@@ -37,5 +37,4 @@ function kernel(prob::BackSubstitutionProblem)
     return BackSubstitutionSolution(x)
 end
 
-
-export BackSubstitution, kernel
+export BackSubstitution, kernel

src/forward_substitution.jl

@@ -34,5 +34,4 @@ function kernel(prob::ForwardSubstitutionProblem)
     return ForwardSubstitutionSolution(x)
 end
 
-
 export ForwardSubstitution, kernel