Remove n function arguments from the stack
variable args = __pop_args(Integer_Type n);
This function together with the companion function __push_args
is useful for passing the arguments of a function to another function.
__pop_args returns an array of n structures with a
single structure field called value, which represents the value
of the argument.
Consider the following print function. It prints all its
arguments to stdout separated by spaces:
define print ()
{
variable i;
variable args = __pop_args (_NARGS);
for (i = 0; i < _NARGS; i++)
{
() = fputs (string (args[i].value), stdout);
() = fputs (" ", stdout);
}
() = fputs ("\n", stdout);
() = fflush (stdout);
}
ones
that returns a multi-dimensional array with all the elements set to
1. For example, ones(10) should return a 1-d array of ones,
whereas ones(10,20) should return a 10x20 array.
define ones ()
{
!if (_NARGS) return 1;
variable a;
a = __pop_args (_NARGS);
return @Array_Type (Integer_Type, [__push_args (a)]) + 1;
}
__push_args was used to push on the arguments passed to
the ones function onto the stack to be used when dereferencing
Array_Type.
__push_args, typeof, _pop_n
Remove n function arguments onto the stack
__push_args (Struct_Type args);
This function together with the companion function __pop_args
is useful for passing the arguments of one function to another.
See the desription of __pop_args for more information.
__pop_args, typeof, _pop_n
Remove objects from the stack
_pop_n (Integer_Type n);
The _pop_n function pops n objects from the top of the
stack.
define add3 ()
{
variable x, y, z;
if (_NARGS != 3)
{
_pop_n (_NARGS);
error ("add3: Expecting 3 arguments");
}
(x, y, z) = ();
return x + y + z;
}
_stkdepth, pop
print the values on the stack.
_print_stack ()
This function dumps out what is currently on the S-lang. It does not alter the stack and it is usually used for debugging purposes.
_stkdepth, string
Reverse the order of the objects on the stack.
_stk_reverse (Integer_Type n)
The _stk_reverse function reverses the order of the top
n items on the stack.
_stkdepth, _stk_roll
Roll items on the stack
_stk_roll (Integer_Type n);
This function may be used to alter the arrangement of objects on the
stack. Specifically, if the integer n is positive, the top
n items on the stack are rotated up. If
n is negative, the top abs(n) items on the stack are
rotated down.
If the stack looks like:
item-0
item-1
item-2
item-3
item-0 is at the top of the stack, then
_stk_roll(-3) will change the stack to:
item-2
item-0
item-1
item-3
This function only has an effect for abs(n) > 1.
_stkdepth, _stk_reverse, _pop_n, _print_stack
Get the number of objects currently on the stack.
Integer_Type _stkdepth ()
The _stkdepth function returns number of items on stack prior
to the call of _stkdepth.
_print_stack, _stk_reverse, _stk_roll
Duplicate the value at the top of the stack
dup ()
This function returns an exact duplicate of the object on top of the stack. For some objects such as arrays or structures, it creates a new reference to the array. However, for simple scalar S-Lang types such as strings, integers, and doubles, it creates a new copy of the object.
pop, typeof
Exchange two items on the stack
exch ()
The exch swaps the two top items on the stack.
pop, _stk_reverse, _stk_roll
Discard an item from the stack
pop ()
The pop function removes the top item from the stack.
_pop_n