1 files changed, 77 insertions, 0 deletions
diff --git a/bu-parser.h b/bu-parser.h
new file mode 100644
index 0000000..0aff194
--- /dev/null
+++ b/bu-parser.h
@@ -0,0 +1,77 @@
+#ifndef BU_PARSER_HG
+#define BU_PARSER_HG
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include "tree.h"
+
+/* PRODUCTION RULES
+
+  <expr> ::= <expr> <binary_op> <expr> | <unary_op> <expr> | <var>
+  <binary_op> ::= "*" | "+"
+  <unary_op> ::= "!"
+  <var> ::= r#[a-z]
+
+ */
+
+/* POSSIBILITIES
+  a-z => var
+  
+ */
+
+enum parser_state {
+  PARSER_ERR = -1,
+  PARSER_READY = 0,
+  PARSER_OR_OP,
+  PARSER_AND_OP,
+  PARSER_NOT_OP,
+  PARSER_OK,
+};
+
+enum token_id {
+  TOKEN_INVALID = 0,
+  TOKEN_BINARY_OPERATOR,
+  TOKEN_UNARY_OPERATOR,
+  TOKEN_VARIABLE,
+  TOKEN_EOS,
+  TOKEN_OOB,
+  TOKEN_MAX,
+};
+
+enum stackmember_id {
+  // all token ids
+  STACKMEMBER_INVALID = TOKEN_INVALID,
+  // ...
+  STACKMEMBER_EXPR = TOKEN_MAX + 1,
+  STACKMEMBER_MAX,
+};
+
+struct chartoken { enum token_id id; char c; };
+typedef struct chartoken(*lexer_fn)(void*);
+
+struct stackmember {
+  enum stackmember_id id;
+  union {
+    char terminal;
+    node *expr;
+  };
+};
+
+struct expr_parser {
+  lexer_fn lex;
+  void *lex_data;
+  // since tokens are 1-to-1 maps to chars,
+  // we're fine making this type assumption
+  struct chartoken lahead;
+  enum parser_state st;
+  // (and 1024 oughta be enough, FIXME if not)
+  struct stackmember stack[1024];
+  size_t stack_idx;
+};
+
+struct expr_parser expr_parser_init(lexer_fn src, void* lex_data);
+void expr_parser_finish(struct expr_parser *ep);
+int expr_parser_run(struct expr_parser *ep);
+
+#endif // BU_PARSER_HG