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// Copyright (c) 2024, Marvin Borner <dev@marvinborner.de>
// SPDX-License-Identifier: MIT
#include <log.h>
#include <impl.h>
static void encode(Term *term, FILE *fp)
{
switch (term->type) {
case ABS:
while (1) {
fprintf(fp, "0");
if (term->u.abs.body->type != ABS)
break;
term = term->u.abs.body;
}
fprintf(fp, "01");
encode(term->u.abs.body, fp);
break;
case APP:
fprintf(fp, "01");
encode(term->u.app.lhs, fp);
encode(term->u.app.rhs, fp);
break;
case IDX:
for (size_t i = 0; i <= term->u.index; i++)
fprintf(fp, "1");
fprintf(fp, "0");
break;
default:
fatal("invalid type %d\n", term->type);
}
}
static Term *decode(FILE *fp)
{
Term *res = 0;
char a = getc(fp);
if (a == '0') {
size_t count = 0;
while (getc(fp) == '0')
count++;
if (count == 0) {
res = term_new(APP);
res->u.app.lhs = decode(fp);
res->u.app.rhs = decode(fp);
} else {
Term *head = term_new(ABS);
res = head;
for (size_t i = 0; i < count - 1; i++) {
res->u.abs.body = term_new(ABS);
res = res->u.abs.body;
}
res->u.abs.body = decode(fp);
res = head;
}
} else if (a == '1') {
res = term_new(IDX);
res->u.index = 0;
while (getc(fp) == '1')
res->u.index++;
}
if (!res)
fatal("invalid parsing state!\n");
return res;
}
Impl impl_abs(void)
{
return (Impl){
.name = "abs",
.encode = encode,
.decode = decode,
};
}
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