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// Copyright (c) 2024, Marvin Borner <dev@marvinborner.de>
// SPDX-License-Identifier: MIT
// TODO: Instead of unsharing open entries, they could be abstracted into closed terms
// and then resubstituted using the Jedi spaceship invasion technique.
// This would only help in very rare edge cases though
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <target.h>
#include <parse.h>
#include <log.h>
#define META_CLOSED 0x1
#define META_OPEN 0x2
static void fprint_blc_substituted(struct term *term, struct bloc_parsed *bloc,
size_t *positions_inv, void **closed,
int depth, FILE *file)
{
switch (term->type) {
case ABS:
fprintf(file, "00");
fprint_blc_substituted(term->u.abs.term, bloc, positions_inv,
closed, depth + 1, file);
break;
case APP:
fprintf(file, "01");
fprint_blc_substituted(term->u.app.lhs, bloc, positions_inv,
closed, depth, file);
fprint_blc_substituted(term->u.app.rhs, bloc, positions_inv,
closed, depth, file);
break;
case VAR:
for (int i = 0; i <= term->u.var.index; i++)
fprintf(file, "1");
fprintf(file, "0");
break;
case REF:
if (term->u.ref.index + 1 >= bloc->length)
fatal("invalid ref index %ld\n", term->u.ref.index);
int reffed = bloc->length - term->u.ref.index - 2;
if (closed[reffed]) {
debug("closed ref %d\n", reffed);
int index = depth + positions_inv[reffed];
for (int i = 0; i <= index; i++)
fprintf(file, "1");
fprintf(file, "0");
} else {
fprint_blc_substituted(bloc->entries[reffed], bloc,
positions_inv, closed, depth,
file);
}
break;
default:
fatal("invalid type %d\n", term->type);
}
}
static void fprint_blc(size_t *positions, void *closed,
struct bloc_parsed *bloc, FILE *file)
{
size_t *positions_inv =
calloc(bloc->length * sizeof(*positions_inv), 1);
size_t end = 0;
for (size_t i = 0; i < bloc->length; i++) {
if (!positions[i]) {
end = i;
break;
}
positions_inv[bloc->length - positions[i]] = i;
fprintf(file, "0100"); // ([
/* fprintf(file, "(["); */
}
/* fprintf(file, "0"); */
for (size_t i = end; i > 0; i--) {
/* fprintf(file, "]"); // implicit */
fprint_blc_substituted(
bloc->entries[bloc->length - positions[i - 1]], bloc,
positions_inv, closed, 0, file);
/* fprintf(file, "<%ld>", bloc->length - positions[i - 1]); */
/* fprintf(file, ")"); // implicit */
}
free(positions_inv);
}
static void bitmap_deps(struct bloc_parsed *bloc, char *bitmap,
struct term *term)
{
switch (term->type) {
case ABS:
bitmap_deps(bloc, bitmap, term->u.abs.term);
break;
case APP:
bitmap_deps(bloc, bitmap, term->u.app.lhs);
bitmap_deps(bloc, bitmap, term->u.app.rhs);
break;
case VAR:
break;
case REF:
if (term->u.ref.index + 1 >= bloc->length)
fatal("invalid ref index %ld\n", term->u.ref.index);
bitmap[bloc->length - term->u.ref.index - 2] = 1;
break;
default:
fatal("invalid type %d\n", term->type);
}
}
// TODO: memoize META_CLOSED with term->meta (more complex than you'd think!)
static unsigned int annotate(struct bloc_parsed *bloc, struct term *term,
int depth)
{
switch (term->type) {
case ABS:
return annotate(bloc, term->u.abs.term, depth + 1);
case APP:;
unsigned int left = annotate(bloc, term->u.app.lhs, depth);
unsigned int right = annotate(bloc, term->u.app.rhs, depth);
if ((left & META_OPEN) || (right & META_OPEN))
return META_OPEN;
return META_CLOSED;
case VAR:
if (term->u.var.index >= depth)
return META_OPEN;
return META_CLOSED;
case REF:
if (term->u.ref.index + 1 >= bloc->length)
fatal("invalid ref index %ld\n", term->u.ref.index);
struct term *sub =
bloc->entries[bloc->length - term->u.ref.index - 2];
return annotate(bloc, sub, depth);
default:
fatal("invalid type %d\n", term->type);
}
}
#define PERMANENT_MARK 0x1
#define TEMPORARY_MARK 0x2
static void visit(char **bitmaps, char *marks, size_t *positions,
size_t *position, size_t length, size_t n)
{
if (!bitmaps[n]) {
marks[n] |= PERMANENT_MARK;
return;
}
if (marks[n] & PERMANENT_MARK)
return;
if (marks[n] & TEMPORARY_MARK)
fatal("dependency graph has a cycle (infinite term)\n");
marks[n] |= TEMPORARY_MARK;
for (size_t i = 0; i < length; i++) {
if (bitmaps[n][i]) {
visit(bitmaps, marks, positions, position, length, i);
}
}
marks[n] &= ~TEMPORARY_MARK;
marks[n] |= PERMANENT_MARK;
positions[*position] = length - n; // deliberate offset of +2
(*position)++;
}
static size_t *topological_sort(char **bitmaps, size_t length)
{
char *marks = calloc(length, 1);
size_t *positions = calloc(length * sizeof(*positions), 1);
size_t position = 0;
int marked = 1;
while (marked) { // TODO: outer loop can be removed?
marked = 0;
for (size_t i = 0; i < length; i++) {
if ((marks[i] & PERMANENT_MARK) == 0)
marked = 1; // still has nodes without permanent
if (marks[i] & 0x3)
continue;
visit(bitmaps, marks, positions, &position, length, i);
}
}
free(marks);
return positions;
}
static void write_blc(struct bloc_parsed *bloc, FILE *file)
{
char **bitmaps = malloc(bloc->length * sizeof(*bitmaps));
for (size_t i = 0; i < bloc->length; i++) {
unsigned int meta = annotate(bloc, bloc->entries[i], 0);
if (!(meta & META_CLOSED)) {
bitmaps[i] = 0;
continue;
}
char *bitmap = calloc(bloc->length, 1);
bitmap_deps(bloc, bitmap, bloc->entries[i]);
bitmaps[i] = bitmap;
}
size_t *positions = topological_sort(bitmaps, bloc->length);
fprint_blc(positions, bitmaps, bloc, file);
/* fprintf(file, "\n"); */
for (size_t i = 0; i < bloc->length; i++) {
/* printf("%ld: %ld, ", i, positions[i]); */
if (bitmaps[i])
free(bitmaps[i]);
}
free(bitmaps);
free(positions);
}
struct target_spec target_blc = {
.name = "blc",
.exec = write_blc,
};
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