2 files changed, 67 insertions, 0 deletions
diff --git a/21sh/ll-expr/src/ast/ast.c b/21sh/ll-expr/src/ast/ast.c
new file mode 100644
index 0000000..701d40e
--- /dev/null
+++ b/21sh/ll-expr/src/ast/ast.c
@@ -0,0 +1,27 @@
+#include "ast.h"
+
+#include <err.h>
+#include <stdlib.h>
+
+struct ast *ast_new(enum ast_type type)
+{
+    struct ast *new = calloc(1, sizeof(struct ast));
+    if (!new)
+        return NULL;
+    new->type = type;
+    return new;
+}
+
+void ast_free(struct ast *ast)
+{
+    if (ast == NULL)
+        return;
+
+    ast_free(ast->left);
+    ast->left = NULL;
+
+    ast_free(ast->right);
+    ast->right = NULL;
+
+    free(ast);
+}
diff --git a/21sh/ll-expr/src/ast/ast.h b/21sh/ll-expr/src/ast/ast.h
new file mode 100644
index 0000000..01e0064
--- /dev/null
+++ b/21sh/ll-expr/src/ast/ast.h
@@ -0,0 +1,40 @@
+#ifndef AST_H
+#define AST_H
+
+#include <unistd.h>
+
+enum ast_type
+{
+    AST_PLUS,
+    AST_MINUS,
+    AST_MUL,
+    AST_DIV,
+    AST_NUMBER,
+    AST_NEG
+};
+
+/**
+ * This very simple AST structure should be sufficient for a simple AST.
+ * It is however, NOT GOOD ENOUGH for more complicated projects, such as a
+ * shell. Please read the project guide for some insights about other kinds of
+ * ASTs.
+ */
+struct ast
+{
+    enum ast_type type; // The kind of node we're dealing with
+    ssize_t value; // If the node is a number, it stores its value
+    struct ast *left; // The left branch if any, unary or binary
+    struct ast *right; // The right branch of the binary node
+};
+
+/**
+ ** \brief Allocates a new ast with the given type.
+ */
+struct ast *ast_new(enum ast_type type);
+
+/**
+ ** \brief Recursively frees the given ast.
+ */
+void ast_free(struct ast *ast);
+
+#endif /* !AST_H */