1 files changed, 124 insertions, 0 deletions
diff --git a/print-regex.c b/print-regex.c
new file mode 100644
index 0000000..02a58fa
--- /dev/null
+++ b/print-regex.c
@@ -0,0 +1,124 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "ast.h"
+
+static const int precedence[ATOM_MAX] = {
+	[ATOM_ALPHABETIC]  = 1,
+	[ATOM_NUMERIC]     = 1,
+	[ATOM_UPPERCASE]   = 1,
+	[ATOM_LOWERCASE]   = 1,
+	[ATOM_CONTROL]     = 1,
+	[ATOM_PUNCTUATION] = 1,
+	[ATOM_EVERYTHING]  = 1,
+	[ATOM_REPETITION]  = 2,
+	[ATOM_SEQUENCE]    = 3,
+	[ATOM_LITERAL]     = 3,
+	[ATOM_ALTERNATION] = 4,
+};
+
+static void print_repeat(const struct repeat *r)
+{
+	if (r->max < 0) {
+		switch (r->min) {
+		case 0:  printf("*"); break;
+		case 1:  printf("+"); break;
+		default: printf("{%ld,}", r->min); break;
+		}
+	} else if (r->min == 0 && r->max == 1) {
+		printf("?");
+	} else if (r->min == r->max) {
+		printf("{%ld}", r->min);
+	} else {
+		printf("{%ld,%ld}", r->min, r->max);
+	}
+}
+
+static void print_literal(const char *s)
+{
+	for (; *s; s++) {
+		switch (*s) {
+		case '.':
+		case '[':
+		case '{':
+		case '}':
+		case '(':
+		case ')':
+		case '\\':
+		case '*':
+		case '+':
+		case '?':
+		case '|':
+		case '^':
+		case '$':
+			putchar('\\');
+
+		default:
+			putchar(*s);
+		}
+	}
+}
+
+static int get_precedence(const struct atom *a)
+{
+	if (a->type == ATOM_LITERAL) {
+		switch (strlen(a->u.literal)) {
+		case 0:  return -1;
+		case 1:  return precedence[ATOM_EVERYTHING];
+		default: return precedence[ATOM_SEQUENCE];
+		}
+	}
+
+	return precedence[a->type];
+}
+
+static void print_atom(const struct atom *a);
+
+static void print_child_atom(const struct atom *child, const struct atom *parent)
+{
+	int group = get_precedence(child) > get_precedence(parent);
+	if (group) printf("(");
+	print_atom(child);
+	if (group) printf(")");
+}
+
+static void print_atom(const struct atom *a)
+{
+	switch (a->type) {
+	case ATOM_ALTERNATION:
+		print_child_atom(a->u.children[0], a);
+		printf("|");
+		print_child_atom(a->u.children[1], a);
+		break;
+
+	case ATOM_SEQUENCE:
+		print_child_atom(a->u.children[0], a);
+		print_child_atom(a->u.children[1], a);
+		break;
+
+	case ATOM_REPETITION:
+		print_child_atom(a->u.repeat.child, a);
+		print_repeat(&a->u.repeat.counts);
+		break;
+
+	case ATOM_LITERAL:
+		print_literal(a->u.literal);
+		break;
+
+	case ATOM_ALPHABETIC:  printf("[:alpha:]"); break;
+	case ATOM_NUMERIC:     printf("[:digit:]"); break;
+	case ATOM_UPPERCASE:   printf("[:upper:]"); break;
+	case ATOM_LOWERCASE:   printf("[:lower:]"); break;
+	case ATOM_CONTROL:     printf("[:cntrl:]"); break;
+	case ATOM_PUNCTUATION: printf("[:punct:]"); break;
+	case ATOM_EVERYTHING:  printf(".");         break;
+	}
+}
+
+void print_regex(const struct atom *a)
+{
+	printf("^");
+	print_atom(a);
+	printf("$\n");
+}
+