WIP LFO implementation

Author: rothmichaels

example/CMakeLists.txt

@@ -71,6 +71,7 @@ add_example(storage_tank)
 add_example(strong_angular_quantities)
 add_example(total_energy)
 add_example(unmanned_aerial_vehicle example_utils)
+add_example(lfo)
 
 add_subdirectory(glide_computer_lib)
 add_subdirectory(kalman_filter)

example/lfo.cpp

@@ -0,0 +1,193 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2024 Roth Michaels
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+// !!! Before you commit any changes to this file please make sure to check if it !!!
+// !!! renders correctly in the documentation "Examples" section.                 !!!
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
+#include <exception>
+#include <iostream>
+#endif
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/ostream.h>
+// #include <mp-units/systems/cgs.h>
+// #include <mp-units/systems/international.h>
+#include <mp-units/systems/angular.h>
+#include <mp-units/systems/isq.h>
+#include <mp-units/systems/si.h>
+#endif
+
+namespace third_party {
+
+//! State of a playback engine for music host application.
+struct musical_context {
+  float sample_rate;  //!< samples per second
+  float tempo;        //!< beats per minute (quarter note == one beat)
+};
+
+//! API provided by music host application to provide global info
+//! about the playback engine.
+musical_context get_musical_context()
+{
+  // Example data, this would be variable in a real-world context
+  return musical_context{.sample_rate = 8000.f, .tempo = 130.f};
+}
+}  // namespace third_party
+
+namespace {
+using namespace mp_units;
+
+QUANTITY_SPEC(sample_count, dimensionless, is_kind);
+QUANTITY_SPEC(sample_duration, isq::time);
+QUANTITY_SPEC(sample_rate, isq::frequency, sample_count / isq::time);
+
+inline constexpr struct sample final : named_unit<"Smpl", one, kind_of<sample_count>> {
+} sample;
+
+QUANTITY_SPEC(unit_sample_amount, dimensionless, is_kind);
+
+inline constexpr struct sample_value final : named_unit<"PCM", one, kind_of<unit_sample_amount>> {
+} sample_value;
+
+QUANTITY_SPEC(beat_count, dimensionless, is_kind);
+QUANTITY_SPEC(beat_duration, isq::time);
+QUANTITY_SPEC(tempo, isq::frequency, beat_count / isq::time);
+
+inline constexpr struct quarter_note final : named_unit<"q", one, kind_of<beat_count>> {
+} quarter_note;
+static_assert(detail::SymbolicArg<struct quarter_note>);
+static_assert(Unit<struct quarter_note>);
+
+inline constexpr struct whole_note final : named_unit<"w", mag<4> * quarter_note> {
+} whole_note;
+inline constexpr struct half_note final : named_unit<"h", mag<2> * quarter_note> {
+} half_note;
+inline constexpr struct dotted_half_note final : named_unit<"h.", mag<3> * quarter_note> {
+} dotted_half_note;
+inline constexpr struct eigth_note final : named_unit<"8th", mag_ratio<1, 2> * quarter_note> {
+} eigth_note;
+inline constexpr struct dotted_quarter_note final : named_unit<"q.", mag<3> * eigth_note> {
+} dotted_quarter_note;
+inline constexpr struct quarter_note_triplet final : named_unit<"qt", mag_ratio<1, 3> * half_note> {
+} quarter_note_triplet;
+inline constexpr struct sixteenth_note final : named_unit<"16th", mag_ratio<1, 2> * eigth_note> {
+} sixteenth_note;
+inline constexpr struct dotted_eigth_note final : named_unit<"8th.", mag<3> * sixteenth_note> {
+} dotted_eigth_note;
+
+inline constexpr struct beats_per_minute final : named_unit<"bpm", quarter_note / non_si::minute> {
+} beats_per_minute;
+
+inline constexpr auto smpl = sample;
+
+inline constexpr auto pcm = sample_value;
+
+// inline constexpr auto n_wd = 3 * half_note;
+inline constexpr auto n_w = whole_note;
+// inline constexpr auto n_hd = dotted_half_note;
+// inline constexpr auto n_h = half_note;
+// inline constexpr auto n_qd = dotted_quarter_note;
+// inline constexpr auto n_q = quarter_note;
+// inline constexpr auto n_qt = quarter_note_triplet;
+// inline constexpr auto n_8thd = dotted_eigth_note;
+// inline constexpr auto n_8th = eigth_note;
+// inline constexpr auto n_16th = sixteenth_note;
+
+// inline constexpr auto bpm = beats_per_minute;
+
+//! Typesafe version of music application playback engine state
+struct musical_context {
+  quantity<sample_rate[si::hertz], float> sample_rate;
+  quantity<beats_per_minute, float> tempo;
+};
+
+//! Typesafe wrapper around API for host application musical context
+musical_context get_musical_context()
+{
+  auto context = third_party::get_musical_context();
+  return musical_context{.sample_rate = context.sample_rate * si::hertz, .tempo = context.tempo * beats_per_minute};
+}
+
+class sine_wave_osc {
+public:
+  sine_wave_osc(const musical_context& context, QuantityOf<isq::frequency> auto freq) :
+      m_context{context}, m_frequency{freq}
+  {
+    std::cout << std::format("Created LFO with starting frequency {} ({}) for sample rate {} at tempo {}\n", freq,
+                             m_frequency, context.sample_rate, context.tempo);
+  }
+
+  quantity<si::hertz, float> get_frequency() const { return m_frequency; }
+
+  void set_frequency(QuantityOf<isq::frequency> auto freq)
+  {
+    m_frequency = freq;
+    std::cout << std::format("Setting frequency to {} ({})\n", freq, m_frequency);
+  }
+
+  void set_period(QuantityOf<isq::time> auto period)
+  {
+    m_frequency = 1.f / period;
+    std::cout << std::format("Setting period to {} (i.e. frequency to {})\n", period, m_frequency);
+  }
+
+  quantity<sample_value, float> operator()()
+  {
+    auto out = sin(m_phase);
+    m_phase += step;
+    return out;
+  }
+
+private:
+  void update_step() { m_step = (angular::revolution * m_frequency) / m_context.sample_rate; }
+
+  quantity<sample_value> sin(quantity_point<angular::radian, float>)
+  {
+    return std::sin(m_phase.numerical_value_in(angular::radian)) * pcm;
+  }
+
+  musical_context m_context;
+  quantity<si::hertz, float> m_frequency;
+  quantity_point<angular::radian, float> m_phase{0.f};
+  quantity<angular::radian, float> m_step;
+};
+}  // namespace
+
+int main()
+{
+  using namespace mp_units::si::unit_symbols;
+
+  const auto context = get_musical_context();
+
+  auto sin_gen = sine_wave_osc{context, 2 * Hz};
+
+  // TODO set_frequency and set_period calls for demonstrating use of different units
+
+
+  auto buffer = std::vector<quantity<sample_value, float>>(2 * whole_note)
+}