LV2 synth in symbol language (typed Clojure dialect)

gistfile1.clj

(ns synth
  (include "cmath" 
           "lv2/lv2plug.in/ns/lv2core/lv2.h"))

(defstruct Synth
  (sample-rate double)
  (phase float)
  (freq float*)
  (output float*))

(defn ^void* instantiate 
  [^LV2_Descriptor.const* descriptor 
   ^double rate 
   ^char.const* bundle-path 
   ^LV2_Feature.const*.const* features]
  (let [self (new Synth)]
    (set! (.sample-rate self) rate)
    self))

(defn connect-port 
  [^LV2_Handle instance ^uint port ^void* data]
  (let [self (cast Synth* instance)]
    (match port
           (uint 0) (set! (.freq self) (cast float* data))
           (uint 1) (set! (.output self) (cast float* data)))))

(defn activate
  [^LV2_Handle instance]
  (let [self (cast Synth* instance)]
    (set! (.phase self) (float 0.0))))

(defn run
  [^LV2_Handle instance ^uint32_t n-samples]
  (let [self (cast Synth* instance)
        PI (float 3.1415)
        volume (float 0.3)
        freq (pref (.freq self))
        output (.output self)
        samples-per-cycle (/ (float (.sample-rate self)) freq)
        phase-increment (/ (float 1.0) samples-per-cycle)]
    (dotimes [pos (long n-samples)]
      (pset! output pos (* (sin (* (.phase self) (float 2.0) PI)) volume))
      (set! (.phase self) (+ (.phase self) phase-increment))
      (if (> (.phase self) (float 1.0))
        (set! (.phase self) (float 0.0))))))

(defn deactivate 
  [^LV2_Handle instance])
        
(defn cleanup
  [^LV2_Handle instance]
  (delete (cast Synth* instance)))

(defn ^void.const* extension-data
  [^char.const* uri]
  nil)

(extern "C"
"
/** The LV2_Descriptor for this plugin. */
static const LV2_Descriptor descriptor = {
    \"http://lv2plug.in/plugins/eg-synth\",
    instantiate,
    connect_port,
    activate,
    run,
    deactivate,
    cleanup,
    extension_data
};

LV2_SYMBOL_EXPORT
const LV2_Descriptor*
lv2_descriptor(uint32_t index) {
    switch (index) {
        case 0:  return &descriptor;
        default: return 0;
    }
}")
                                  
  

The symbol project is located here https://github.com/timowest/symbol

symbol is very much in alpha stage

There are lots of literal casts, since symbol supports currently only double and long number literals, like Clojure.

Also the const flags are a bit ugly, comment here if you have improvement suggestions timowest/symbol#25