GNU Astronomy Utilities


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10.3.7.4 List of float

Single precision floating point numbers can accurately store real number until 7.2 decimals and only consume 4 bytes (32-bits) of memory, see Numeric data types. Since astronomical data rarely reach that level of precision, single precision floating points are the type of choice to keep and read data. However, when processing the data, it is best to use double precision floating points (since errors propagate).

Type (C struct): gal_list_f32_t

A single node in a list containing a 32-bit single precision float value: see Numeric data types.

typedef struct gal_list_f32_t
{
  float v;
  struct gal_list_f32_t *next;
} gal_list_f32_t;
Function:
void
gal_list_f32_add (gal_list_f32_t **list, float value)

Add a new node (containing value) to the top of the list of floats and update list. Here is one short example of initializing and adding elements to a string list:

gal_list_f32_t *flist=NULL;
gal_list_f32_add(&flist, 3.89);
gal_list_f32_add(&flist, 1.23e-20);
Function:
float
gal_list_f32_pop (gal_list_f32_t **list)

Pop the top element of list and return the value. This function will also change list to point to the next node in the list. If *list==NULL, then this function will return GAL_BLANK_FLOAT32 (NaN, see Library blank values (blank.h)).

Function:
size_t
gal_list_f32_number (gal_list_f32_t *list)

Return the number of nodes in list.

Function:
void
gal_list_f32_print (gal_list_f32_t *list)

Print the values within each node of *list on the standard output in the same order that they are stored. Each floating point number is printed on one line. This function is mainly good for checking/debugging your program. For program outputs, its best to make your own implementation with a better, more user-friendly format. For example, in the following code snippet. You can also modify it to print all values in one line, and etc, depending on the context of your program.

size_t i;
gal_list_f32_t *tmp;
for(tmp=list; tmp!=NULL; tmp=tmp->next)
  printf("Node %zu: %f\n", i, tmp->v);
Function:
void
gal_list_f32_reverse (gal_list_f32_t **list)

Reverse the order of the list such that the top node in the list before calling this function becomes the bottom node after it.

Function:
float *
gal_list_f32_to_array (gal_list_f32_t *list, int reverse, size_t *num)

Dynamically allocate an array and fill it with the values in list. The function will return a pointer to the allocated array and put the number of elements in the array into the num pointer. If reverse has a non-zero value, the array will be filled in the inverse of the order of elements in list. This function can be useful after you have finished reading an initially unknown number of values and want to put them in an array for easy random access.

Function:
void
gal_list_f32_free (gal_list_f32_t *list)

Free every node in list.


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