Multimethods are fantastic and do indeed work across namespaces if by
"across namespaces" you mean you can defmethod in ns2 a defmulti in ns1.
On Tuesday, April 15, 2014 2:56:30 AM UTC+1, Andrew Chambers wrote:
>
> An update, I read about protocols and multimethods. I think multimethods
> are a decent way to go (cant use protocols without a defrecord) provided
> they work across namespaces.
>
> On Tuesday, April 15, 2014 11:52:36 AM UTC+12, Andrew Chambers wrote:
>>
>> Hi everyone,
>>
>> I'm new to clojure and in order to learn I'm working on making some
>> compiler tools which converts a lightweight IR code into assembly.
>>
>> My data model for an IR function is along the lines of
>> (def code
>> {
>> :entry
>> [[:loadaddr :x "global_label"]
>> [:loadconst 1 :y]
>> [:add :x :y :z]
>> [:jmp :exit]]
>> :exit
>> [[:ret :z]]
>> })
>>
>> This, when translated to assembly and after register allocation would
>> turn into something like (ignoring calling conventions etc):
>> (def assembly-code
>> {
>> :entry
>> [[:x86.lea :eax "global_label"]
>> [:x86.loadimm 1, :eax]
>> [:x86.add32 :ebx :eax]
>> [:jmp :exit]]
>> :exit
>> [[:ret]]
>> })
>>
>> The problem arises when I have to query the IR code for things like
>> accesses-memory? or get-output-vars in an
>> extensible way so that multiple target architectures can be supported.
>> e.g. (get-output-vars [:add :a :b :c]) -> :c
>> (get-output-vars [:x86.add :a :b]) -> :b ;; the input and output
>> positions are opcode specific
>> (get-output-vars [:x86.add :a :b]) -> :b
>> (get-output-vars [:divmod :a :b :c :d]) -> :c :d
>> (accesses-memory? :x86.add) -> false
>> (accesses-memory? :x86.load) -> true
>> (accesses-memory? :loadconst) ->false
>> I have to be able to write these functions in a way that knows about the
>> format of the basic IR opcodes, but can also be extended
>> to handle opcodes of architectures that don't exist in my code yet, the
>> extensions would exist within the namespaces of that specific architecture
>> and shouldn't need to modify the code for the built in opcodes.
>>
>> What is the most seamless and efficient way to achieve this sort of
>> function extension in clojure? Also, how would I allow sharing
>> of implementations where instructions have similar layouts.
>>
>> e.g.
>> (get-output-vars [:add :a :b :c]) -> :c
>> (get-output-vars [:sub :a :b :c]) -> :c
>>
>>
>>
>>
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