From 033d377a30b07cd94515f5f9ff847554ca58dc2a Mon Sep 17 00:00:00 2001
From: Wouter Deconinck <wdconinc@gmail.com>
Date: Sun, 31 Dec 2023 17:26:01 -0600
Subject: [PATCH] fix: add default parameters to random distributions (requires
 C++20)

This adds constraints for integral and floating point types to make sure that
default parameter values are well-defined. Instead of `gaussian(0.,1.)`, we
can now also use `gaussian()` with the same effect. This reduces the need to
specify constants where they can be easily swapped, e.g. mu and sigma.
---
 core/include/algorithms/random.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/core/include/algorithms/random.h b/core/include/algorithms/random.h
index 1c7d112..bc588dc 100644
--- a/core/include/algorithms/random.h
+++ b/core/include/algorithms/random.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <concepts>
 #include <cstdint>
 #include <functional>
 #include <mutex>
@@ -26,27 +27,27 @@ class Generator {
 public:
   Generator(const RandomEngineCB& gen, const size_t cache_size) : m_gen{gen, cache_size} {}
 
-  template <class Int = int> Int uniform_int(const Int min, const Int max) const {
+  template <std::integral Int = int> Int uniform_int(const Int min = 0, const Int max = 1) const {
     std::uniform_int_distribution<Int> d{min, max};
     std::lock_guard<std::mutex> lock{m_mutex};
     return d(m_gen);
   }
-  template <class Float = double> Float uniform_double(const Float min, const Float max) const {
+  template <std::floating_point Float = double> Float uniform_double(const Float min = 0, const Float max = 1) const {
     std::uniform_real_distribution<Float> d{min, max};
     std::lock_guard<std::mutex> lock{m_mutex};
     return d(m_gen);
   }
-  template <class Int = int> Int poisson(const Int mean) const {
+  template <std::integral Int = int> Int poisson(const Int mean = 1) const {
     std::poisson_distribution<Int> d{mean};
     std::lock_guard<std::mutex> lock{m_mutex};
     return d(m_gen);
   }
-  template <class Float = double> Float exponential(const Float lambda) const {
+  template <std::floating_point Float = double> Float exponential(const Float lambda = 1) const {
     std::exponential_distribution<Float> d{lambda};
     std::lock_guard<std::mutex> lock{m_mutex};
     return d(m_gen);
   }
-  template <class Float = double> Float gaussian(const Float mu, const Float sigma) const {
+  template <std::floating_point Float = double> Float gaussian(const Float mu = 0, const Float sigma = 1) const {
     std::normal_distribution<Float> d{mu, sigma};
     std::lock_guard<std::mutex> lock{m_mutex};
     return d(m_gen);