From 5a2f6687f681fa0ceff19a42ec9ddce479e67c48 Mon Sep 17 00:00:00 2001
From: Pedro Souza <pedro@masba.net>
Date: Thu, 4 Apr 2024 01:52:22 -0300
Subject: added truth table and expression evaluator

---
 truth_table.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 truth_table.c

(limited to 'truth_table.c')

diff --git a/truth_table.c b/truth_table.c
new file mode 100644
index 0000000..9ae9463
--- /dev/null
+++ b/truth_table.c
@@ -0,0 +1,77 @@
+#include "truth_table.h"
+
+int intpow(int b, int e) {
+  int acc = 1;
+  for (int i = 0; i < e; i++) {
+    acc *= b;
+  }
+  return acc;
+}
+
+struct expr_input_iter expr_input_iter_init(struct truth_table *tt) {
+  return (struct expr_input_iter){
+    .src = tt,
+    .acc = 0,
+    .count = 0,
+  };
+}
+
+int32_t expr_input_iter_next(struct expr_input_iter *self) {
+  uint32_t bak = self->acc;
+  if (self->count > self->src->lines_count-1) return -1;
+  for (int i = self->src->letters_count - 1; i >= 0; i--) {
+    uint8_t idx = self->src->letters[i] - 'a';
+    self->acc ^= 1 << idx;
+    if (self->acc & (1 << idx)) break;
+  }
+  self->count++;
+  return bak;
+}
+
+struct truth_table *truth_table_create(node *root, uint32_t letters_bitfield) {
+  struct truth_table *tt = calloc(1, sizeof(struct truth_table));
+  char letters[27] = {0};
+  char letters_needle = 0;
+  for (char i = 0; i <= ('z'-'a'); i++) {
+    if (letters_bitfield & (1 << i)) {
+      letters[letters_needle] = 'a'+i;
+      letters_needle++;
+    }
+  }
+  tt->letters = malloc(letters_needle * sizeof(char));
+  strncpy(tt->letters, letters, letters_needle);
+  tt->letters_count = letters_needle;
+  tt->lines_count = intpow(2,tt->letters_count);
+  tt->lines = malloc(tt->lines_count * sizeof(uint32_t));
+
+  struct expr_input_iter inp_iter = expr_input_iter_init(tt);
+  for (int i = 0; i < tt->lines_count; i++) {
+    int32_t input = expr_input_iter_next(&inp_iter);
+    uint8_t output = eval_tree(root, input);
+    tt->lines[i] = input | (output << 26);
+  }
+
+  return tt;
+}
+
+void truth_table_destroy(struct truth_table *tt) {
+  free(tt->lines);
+  free(tt->letters);
+  free(tt);
+}
+
+void truth_table_fprint(FILE *stream, struct truth_table *tt) {
+  fprintf(stream, "\t%s | S\n\t", tt->letters);
+  for (int i = 0; i < (tt->letters_count + 4); i++) putc('-', stream);
+  putc('\n', stream);
+  for (int i = 0; i < tt->lines_count; i++) {
+    putc('\t', stream);
+    uint32_t line = tt->lines[i];
+    for (int j = 0; j < tt->letters_count; j++) {
+      int actual_idx = tt->letters[j] - 'a';
+      putc((line & (1 << actual_idx))? '1' : '0', stream);
+    }
+    fprintf(stream, " | %c\n", (line & (1 << 26))? '1' : '0');
+  }
+}
+
-- 
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