Argument Unpacking Helpers

Variadic helpers for extracting arguments from x-lang arg lists. More...

Functions
static void	__attribute__ ((unused)) x_args(x_obj_t *p_base
	va_start (ap, count)
	for (i=0;i< count;i++)
	va_end (ap)
	x_heap_root_push (p_cell, roots[0])
	x_heap_root_push (p_cell, roots[1])
	x_heap_root_pop (p_cell)

Variables
static void x_obj_t *	p_args
static void x_obj_t int	count
static void x_obj_t int int	i
int	held = 0
x_obj_t **	p_cell = x_heap_root_slot(p_base)
x_spair_t	roots [2]

Detailed Description

Variadic helpers for extracting arguments from x-lang arg lists.

Function Documentation

__attribute__()

static x_obj_t __attribute__ ( (unused)  )

static

Unpack count elements from an args list into output pointers.

NULL pointers skip that position (like _ in pattern matching).

x_args(p_base, p_args, 3, NULL, &a, &b);  // skip self, extract 2

Parameters

p_base	Base/execution context (for the improper-spine raise).
p_args	Argument list (pair chain).
count	Number of positions to unpack.
...	Pointers to x_obj_t* slots (or NULL to skip).

Note

Walking off the proper prefix of an IMPROPER list used to read the tail atom's value word as a pair pointer (#487). The nil test below ends a proper list; x_eval_spine_guard raises on the atom a dotted tail ends with, which is the same catchable error an applicative already gave for a call with a dotted tail.

Unpack and evaluate count elements from an args list.

NULL pointers skip that position without evaluating.

x_eargs(p_base, p_args, 3, NULL, &a, &b);  // skip self, eval+extract 2

Parameters

p_base	Base/execution context.
p_args	Argument list (pair chain).
count	Number of positions to unpack.
...	Pointers to x_obj_t* slots (or NULL to skip).

The args list past its first count positions, or nil if it is shorter.

For a prim that unpacks a fixed prefix with x_args/x_eargs and then takes the tail as a body or a variadic rest. Walking there with x_11/x_111 reads rest of nil when the call is short – (fn), (eval) – which is a SIGSEGV where x_args had already stopped at the end.

Parameters

p_base	Base/execution context (for the improper-spine raise).
p_args	Argument list (pair chain).
count	Number of positions to skip.

Returns

The remaining list, or nil.

for()

for

(

)

va_end()

va_end

(

ap

)

va_start()

va_start	(	ap	,
		count
	)

x_heap_root_pop()

x_heap_root_pop

(

p_cell

)

x_heap_root_push() [1/2]

x_heap_root_push	(	p_cell	,
		roots	[0]
	)

x_heap_root_push() [2/2]

x_heap_root_push	(	p_cell	,
		roots	[1]
	)

Variable Documentation

count

static x_obj_t x_obj_t int count

Initial value:

{
    while (count-- > 0 && p_args != NULL) {
        x_eval_spine_guard(p_base, p_args); 
        p_args = x_restobj(p_args);
    }
    return p_args

held

int held = 0

i

static void x_obj_t int int i

Initial value:

{
    va_list ap

p_args

static x_obj_t x_obj_t * p_args

p_cell

x_obj_t** p_cell = x_heap_root_slot(p_base)

roots

x_spair_t roots[2]

Initial value:

= {
        x_obj_set((x_obj_t *)x_type_pair_obj, X_OBJ_FLAG_NONE,
            { NULL }, { NULL }),
        x_obj_set((x_obj_t *)x_type_pair_obj, X_OBJ_FLAG_NONE,
            { NULL }, { NULL })
    }