From 46b3d1ed6e2831a42c4cd40d399185a8a72bb029 Mon Sep 17 00:00:00 2001
From: Ven Popov <vencislav.popov@gmail.com>
Date: Sun, 31 Mar 2024 04:49:28 +0200
Subject: [PATCH 1/2] add test showing failure of unary '-'

---
 tests/testthat/test-transformations.R | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tests/testthat/test-transformations.R b/tests/testthat/test-transformations.R
index cf830e2e..46dc7599 100644
--- a/tests/testthat/test-transformations.R
+++ b/tests/testthat/test-transformations.R
@@ -118,3 +118,14 @@ test_that("inverses are applied automatically", {
   expect_equal(density(1/(1/dist_gamma(4, 3)), 0.5), density(dist_gamma(4, 3), 0.5))
 
 })
+
+test_that("unary negation operator works", {
+  dist <- dist_normal(1,1)
+  expect_equal(density(-dist, 0.5), density(dist, -0.5))
+
+  dist <- dist_wrap('norm', mean = 1)
+  expect_equal(density(-dist, 0.5), density(dist, -0.5))
+
+  dist <- dist_student_t(3, mu = 1)
+  expect_equal(density(-dist, 0.5), density(dist, -0.5))
+})

From 2b8ae5e67adf1eddddf85171e2eba1ccae125c60 Mon Sep 17 00:00:00 2001
From: Ven Popov <vencislav.popov@gmail.com>
Date: Sun, 31 Mar 2024 04:55:33 +0200
Subject: [PATCH 2/2] allow unary '-' operator on any distribution

---
 NEWS.md         | 5 +++++
 R/default.R     | 5 +++++
 R/transformed.R | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 8e26875d..58bb253d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,10 @@
 # distributional (development version)
 
+## Bug fixes
+
+* Fixed error when using '-' as a unary operator on a distribution different from
+ `dist_normal()` by @venpopov (#95)
+
 # distributional 0.4.0
 
 ## Breaking changes
diff --git a/R/default.R b/R/default.R
index 15249dd1..b855b437 100755
--- a/R/default.R
+++ b/R/default.R
@@ -266,6 +266,11 @@ Math.dist_default <- function(x, ...) {
 #' @method Ops dist_default
 #' @export
 Ops.dist_default <- function(e1, e2) {
+  if(.Generic %in% c("-", "+") && missing(e2)){
+    e2 <- e1
+    e1 <- if(.Generic == "+") 1 else -1
+    .Generic <- "*"
+  }
   is_dist <- c(inherits(e1, "dist_default"), inherits(e2, "dist_default"))
   if(any(vapply(list(e1, e2)[is_dist], dim, numeric(1L)) > 1)){
     stop("Transformations of multivariate distributions are not yet supported.")
diff --git a/R/transformed.R b/R/transformed.R
index aff6c74d..5505e1fa 100755
--- a/R/transformed.R
+++ b/R/transformed.R
@@ -94,6 +94,11 @@ Math.dist_transformed <- function(x, ...) {
 #' @method Ops dist_transformed
 #' @export
 Ops.dist_transformed <- function(e1, e2) {
+  if(.Generic %in% c("-", "+") && missing(e2)){
+    e2 <- e1
+    e1 <- if(.Generic == "+") 1 else -1
+    .Generic <- "*"
+  }
   is_dist <- c(inherits(e1, "dist_default"), inherits(e2, "dist_default"))
   trans <- if(all(is_dist)) {
     if(identical(e1$dist, e2$dist)){