Functional Helpers

The runtime offers a small higher-order toolkit: map, filter, and list comprehensions, driven by C callbacks.

#include "abscom/abs.h"

Callback types

typedef var  (*AbsFunc)(var);
typedef var  (*AbsMapFunc)(var);        /* same shape as AbsFunc */
typedef bool (*AbsFilterFunc)(var);

API

Function	Description
var map_func(var list, AbsFunc f)	New list with f applied to each item.
var filter_func(var list, AbsFunc f)	New list with items for which f(item) is truthy.
var list_comp(var list, AbsMapFunc mapf, AbsFilterFunc filterf)	[map(x) for x in list if filter(x)]; map first, filter second — either may be NULL.

filter_func treats the callback result with the standard truthiness rules. list_comp works on lists and sets; map_func/filter_func require lists.

Example

#include "abscom/abs.h"

static var double_it(var x) {
    return v(x->val.i * 2);
}

static var square_map(var x) {
    return v(x->val.i * x->val.i);
}

static var is_even(var x) {
    return (x->val.i % 2 == 0) ? v(True) : v(False);
}

int main(void) {
    abs_init();

    var xs = range(0, 6);                      /* [0,1,2,3,4,5] */

    var doubled = map_func(xs, double_it);     /* [0,2,4,6,8,10] */
    var evens   = filter_func(xs, is_even);    /* [0,2,4]        */
    var squares = list_comp(xs, square_map, is_even);  /* [0,4,16] */

    print(doubled);
    print(evens);
    print(squares);
    return 0;
}

Notes

• Callbacks receive the element and must return a var. Returning None is fine.
• filter_func and list_comp decide membership with is_true on the filter result — returning v(True)/v(False) is the idiomatic way.
• Read a callback argument's payload with obj->val.i, obj->val.f, or obj->val.s after an is_* check.

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