From 8450f0f8287f5895e0e58e89c789338ae88a1690 Mon Sep 17 00:00:00 2001
From: Andreas Noack <andreas@noack.dk>
Date: Thu, 24 Nov 2022 22:41:00 +0100
Subject: [PATCH] Add a expm1 method for Float16 for older Julia versions

---
 src/distrs/tdist.jl | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/distrs/tdist.jl b/src/distrs/tdist.jl
index 0a56760..0ba04f0 100644
--- a/src/distrs/tdist.jl
+++ b/src/distrs/tdist.jl
@@ -49,13 +49,24 @@ tdistinvcdf(ν::Real, p::Real) = tdistinvcdf(map(float, promote(ν, p))...)
 
 tdistinvccdf(ν::Real, p::Real) = -tdistinvcdf(ν, p)
 
+if VERSION < v"1.7.0-beta1"
+    function _expm1(x::Float16)
+        if -0.2 < x < 0.1
+            return @evalpoly(x, Float16(0), Float16(1), Float16(1/2), Float16(1/6), Float16(1/24), Float16(1/120))
+        else
+            return exp(x) - 1
+        end
+    end
+end
+_expm1(x::Number) = expm1(x)
+
 function tdistinvlogcdf(ν::T, logp::T) where T<:Real
     if isinf(ν)
         return norminvlogcdf(logp)
     elseif logp < -log(2)
         return -sqrt(fdistinvlogccdf(one(ν), ν, logp + log(2*one(logp))))
     else
-        sqrt(fdistinvccdf(one(ν), ν, -2*expm1(logp)))
+        sqrt(fdistinvccdf(one(ν), ν, -2*_expm1(logp)))
     end
 end
 tdistinvlogcdf(ν::Real, logp::Real) = tdistinvlogcdf(map(float, promote(ν, logp))...)