[Ongoing] Rewrite frontend to use Flex/Bison

This is a merge of another experiment, so the changes are large:

- separated "modules" directory into frontend/backend
  - adjusted module names and moved files for this to happen
- removed modules lexer & parser
- removed all the unit tests (most were outdated)
- added Bison, flex, and C development tools to manifest.scm
- added lexer.l, a source file used by the flex utility with a functioning lexing implementation
- added parser.y, a source file used by the bison utility with a functioning parser implementation
- added node.c and node.h, which parser.y uses to construct an AST of a C source file (up to binary ops)
- added driver.c, a Guile-C interface that provides a module to scheme programs
- added a Makefile to make all of this
- added stuff to .gitignore

1 files changed, 84 insertions, 0 deletions

diff --git a/src/frontend/node.c b/src/frontend/node.c
new file mode 100644
index 0000000..344b48a
--- /dev/null
+++ b/src/frontend/node.c
@@ -0,0 +1,84 @@
+#include "node.h"
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+const char* node_types[] = {"prog", "func", "stmt", "expr", "const"};
+const char* node_ops[] = {"not", "neg", "plus", "minus", "mult", "div", "mod"};
+
+Node *create_node(enum node_type type) {
+  Node *node = malloc(sizeof(Node));
+  node->type = type;
+  node->children = NULL;
+  node->num_children = 0;
+  return node;
+}
+
+Node *create_function(char *name) {
+  Node *node = malloc(sizeof(Node));
+  node->type = FUNC;
+  node->field.name = name;
+  node->children = NULL;
+  node->num_children = 0;
+  return node;
+}
+
+Node *create_expr(enum node_op op) {
+  Node *node = malloc(sizeof(Node));
+  node->type = EXPR;
+  node->field.op = op;
+  node->children = NULL;
+  node->num_children = 0;
+  return node;
+}
+
+Node *create_const(int val) {
+  Node *node = malloc(sizeof(Node));
+  node->type = CONST;
+  node->field.val = val;
+  node->children = NULL;
+  node->num_children = 0;
+  return node;
+}
+
+void add_child(Node *parent, Node *child) {
+  size_t new_size = sizeof(Node*) * (parent->num_children + 1);
+  parent->children = realloc(parent->children, new_size);
+
+  parent->children[parent->num_children] = child;
+  parent->num_children++;
+}
+
+void free_node(Node *node) {
+  for (size_t i = 0; i < node->num_children; ++i) {
+    free_node(node->children[i]);
+  }
+  if (node->type == FUNC)
+    free(node->field.name);
+
+  free(node->children);
+  free(node);
+}
+
+void *print_node(Node *node, int indent) {
+  if (node == NULL) {
+    return;
+  }
+
+  for (int i = 0; i < indent; ++i)
+    printf(" ");
+
+  printf("type: %s", node_types[node->type]);
+  if (node->type == FUNC)
+    printf(", name: \"%s\"", node->field.name);
+  if (node->type == EXPR)
+    printf(", op: %s", node_ops[node->field.op]);
+  if (node->type == CONST)
+    printf(", val: %d", node->field.val);
+  printf("\n");
+
+  for (size_t i = 0; i < node->num_children; ++i) {
+    print_node(node->children[i], indent + 1);
+  }
+}