Fix in the procedure remove of chaining hashmaps

src/stdlib_hashmap_chaining.f90

@@ -775,6 +775,7 @@ module subroutine remove_chaining_entry(map, key, existed)
  centry % next => bentry
  map % inverse(inmap) % target => null()
  map % num_free = map % num_free + 1
+ map % num_entries = map % num_entries - 1
 
  end subroutine remove_chaining_entry
 

test/hashmaps/test_maps.fypp

@@ -41,6 +41,7 @@ contains
  , new_unittest("chaining-maps-${hash_}$-${size_}$-byte-words", test_${hash_}$_${size_}$_byte_words) &
  #:endfor
  #:endfor
+ , new_unittest("chaining-maps-removal-spec", test_removal_spec) &
  ]
 
  end subroutine collect_stdlib_chaining_maps
@@ -173,6 +174,55 @@ contains
 
  end subroutine
 
+ subroutine test_removal_spec(error)
+ !! Test following code provided by @jannisteunissen
+ !! https://github.com/fortran-lang/stdlib/issues/785
+ type(error_type), allocatable, intent(out) :: error
+
+ type(chaining_hashmap_type) :: map
+ type(key_type) :: key
+ integer, parameter :: n_max = 500
+ integer :: n
+ integer, allocatable :: key_counts(:)
+ integer, allocatable :: seed(:)
+ integer(int8) :: int32_int8(4)
+ integer(int32) :: keys(n_max)
+ real(dp) :: r_uniform(n_max)
+ logical :: existed, present
+
+ call random_seed(size = n)
+ allocate(seed(n), source = 123456)
+ call random_seed(put = seed)
+
+ call random_number(r_uniform)
+ keys = nint(r_uniform * n_max * 0.25_dp)
+
+ call map%init(fnv_1_hasher, slots_bits=10)
+
+ do n = 1, n_max
+ call set(key, transfer(keys(n), int32_int8))
+ call map%key_test(key, present)
+ if (present) then
+ call map%remove(key, existed)
+ call check(error, existed, "chaining-removal-spec: Key not found in entry removal.")
+ else
+ call map%map_entry(key)
+ end if
+ end do
+
+ ! Count number of keys that occur an odd number of times
+ allocate(key_counts(minval(keys):maxval(keys)), source = 0)
+ do n = 1, n_max
+ key_counts(keys(n)) = key_counts(keys(n)) + 1
+ end do
+ n = sum(iand(key_counts, 1))
+
+ call check(error, map%entries(), n, & 
+ "chaining-removal-spec: Number of expected keys and entries are different.")
+ return
+
+ end subroutine
+
 end module
 
 module test_stdlib_open_maps
@@ -215,6 +265,7 @@ contains
  , new_unittest("open-maps-${hash_}$-${size_}$-byte-words", test_${hash_}$_${size_}$_byte_words) &
  #:endfor
  #:endfor
+ , new_unittest("open-maps-removal-spec", test_removal_spec) &
  ]
 
  end subroutine collect_stdlib_open_maps
@@ -347,6 +398,55 @@ contains
 
  end subroutine
 
+ subroutine test_removal_spec(error)
+ !! Test following code provided by @jannisteunissen
+ !! https://github.com/fortran-lang/stdlib/issues/785
+ type(error_type), allocatable, intent(out) :: error
+
+ type(open_hashmap_type) :: map
+ type(key_type) :: key
+ integer, parameter :: n_max = 500
+ integer :: n
+ integer, allocatable :: key_counts(:)
+ integer, allocatable :: seed(:)
+ integer(int8) :: int32_int8(4)
+ integer(int32) :: keys(n_max)
+ real(dp) :: r_uniform(n_max)
+ logical :: existed, present
+
+ call random_seed(size = n)
+ allocate(seed(n), source = 123456)
+ call random_seed(put = seed)
+
+ call random_number(r_uniform)
+ keys = nint(r_uniform * n_max * 0.25_dp)
+
+ call map%init(fnv_1_hasher, slots_bits=10)
+
+ do n = 1, n_max
+ call set(key, transfer(keys(n), int32_int8))
+ call map%key_test(key, present)
+ if (present) then
+ call map%remove(key, existed)
+ call check(error, existed, "open-removal-spec: Key not found in entry removal.")
+ else
+ call map%map_entry(key)
+ end if
+ end do
+
+ ! Count number of keys that occur an odd number of times
+ allocate(key_counts(minval(keys):maxval(keys)), source = 0)
+ do n = 1, n_max
+ key_counts(keys(n)) = key_counts(keys(n)) + 1
+ end do
+ n = sum(iand(key_counts, 1))
+
+ call check(error, map%entries(), n, & 
+ "open-removal-spec: Number of expected keys and entries are different.")
+ return
+
+ end subroutine
+
 end module