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`size_t`

Positions/sizes in a dataset are conventionally in the `size_t`

type
(see List of `size_t`

) and it sometimes occurs that you want to parse
and read the values in a specific order. For example you want to start from
one pixel and add pixels to the list based on their distance to that
pixel. So that ever time you pop an element from the list, you know it is
the nearest that has not yet been studied. The `gal_list_osizet_t`

type and its functions in this section are designed to facilitate such
operations.

- Type (C
`struct`

):**gal_list_osizet_t** -
Each node in this singly-linked list contains a

`size_t`

value and a floating point value. The floating point value is used as a reference to add new nodes in a sorted manner. At any moment, the first popped node in this list will have the smallest`tosort`

value, and subsequent nodes will have larger to values.

typedef struct gal_list_osizet_t { size_t v; /* The actual value. */ float s; /* The parameter to sort by. */ struct gal_list_osizet_t *next; } gal_list_osizet_t;

- Function:

*void*

**gal_list_osizet_add***(gal_list_osizet_t*`**list`

, size_t`value`

, float`tosort`

) Allocate space for a new node in

`list`

, and store`value`

and`tosort`

into it. The new node will not necessarily be at the “top” of the list. If`*list!=NULL`

, then the`tosort`

values of existing nodes is inspected and the given node is placed in the list such that the top element (which is popped with`gal_list_osizet_pop`

) has the smallest`tosort`

value.

- Function:

*size_t*

**gal_list_osizet_pop***(gal_list_osizet_t*`**list`

, float`*sortvalue`

) Pop a node from the top of

`list`

, return the node’s`value`

and put its sort value in the space that`sortvalue`

points to. This function will also free the allocated space for the popped node and after this function,`list`

will point to the next node (which has a larger`tosort`

element).

- Function:

*void*

**gal_list_osizet_to_sizet_free***(gal_list_osizet_t*`*in`

, gal_list_sizet_t`**out`

) Convert the ordered list of

`size_t`

s into an ordinary`size_t`

linked list. This can be useful when all the elements have been added and you just need to pop-out elements and don’t care about the sorting values any more. After the conversion is done, this function will free the input list. Note that the`out`

list doesn’t have to be empty. If it already contains some nodes, the new nodes will be added on top of them.

GNU Astronomy Utilities 0.4 manual, September 2017.