From fa1600a776cda29a10c6e122872178236495a977 Mon Sep 17 00:00:00 2001
From: Blaise Bourdin <bourdin@mcmaster.ca>
Date: Mon, 19 Oct 2026 11:52:14 -0400
Subject: [PATCH] Fix interval

- left_open and right_open were passed by reference to basic_set_interval,
  which takes them by value, so all intervals were open.
- Absent optional arguments were referenced, because .and. does not short
  circuit. This crashed test_basic when built with fpm.
- The initialization of a_left and a_right implied save, so a closed end
  remained closed in subsequent calls.
---
 src/sets.f90                | 13 +++++++------
 src/symengine_interface.f90 |  2 +-
 test/test_basic.f90         |  6 ++++++
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/sets.f90 b/src/sets.f90
index 822eef9..cc27480 100644
--- a/src/sets.f90
+++ b/src/sets.f90
@@ -67,15 +67,16 @@ function integers() result(res)
 function basic_interval(a, b, left_open, right_open) result(res)
     class(basic), intent(in) :: a, b
     logical, optional :: left_open, right_open
-    integer(c_int) :: a_left = 1, a_right = 1
+    integer(c_int) :: a_left, a_right
     integer(c_long) :: exception
     type(basic) :: res
-    res = Basic()
-    if (present(left_open) .and. .not. left_open) then
-        a_left = 0
+    a_left = 1
+    a_right = 1
+    if (present(left_open)) then
+        if (.not. left_open) a_left = 0
     end if
-    if (present(right_open) .and. .not. right_open) then
-        a_right = 0
+    if (present(right_open)) then
+        if (.not. right_open) a_right = 0
     end if
     res = Basic()
     exception = c_basic_set_interval(res%ptr, a%ptr, b%ptr, a_left, a_right)
diff --git a/src/symengine_interface.f90 b/src/symengine_interface.f90
index bddb9c2..25c94d2 100644
--- a/src/symengine_interface.f90
+++ b/src/symengine_interface.f90
@@ -409,7 +409,7 @@ integer(c_long) function c_basic_set_intersection(s, a, b) bind(c, name='basic_s
     integer(c_long) function c_basic_set_interval(s, start, en, left_open, right_open) bind(c, name='basic_set_interval')
         import :: c_long, c_int, c_ptr
         type(c_ptr), value :: s, start, en
-        integer(c_int) :: left_open, right_open
+        integer(c_int), value :: left_open, right_open
     end function
     integer(c_long) function c_basic_set_finiteset(s, container) bind(c, name='basic_set_finiteset')
         import :: c_long, c_ptr
diff --git a/test/test_basic.f90 b/test/test_basic.f90
index 0804e3c..abb61b1 100644
--- a/test/test_basic.f90
+++ b/test/test_basic.f90
@@ -704,7 +704,13 @@ subroutine test2()
         a = SymInteger(1)
         b = SymInteger(2)
         c = interval(a, b)
+        call assert(c%str() == '(1, 2)')
         c = interval(1, 2, left_open=.true., right_open=.false.)
+        call assert(c%str() == '(1, 2]')
+        c = interval(1, 2, left_open=.false.)
+        call assert(c%str() == '[1, 2)')
+        c = interval(1, 2, right_open=.true.)
+        call assert(c%str() == '(1, 2)')
         c = interval(1, 2_int64)
         c = interval(1_int64, 2)
         c = interval(1_int64, 2_int64)