add expression scaffold

1 files changed, 42 insertions, 0 deletions

diff --git a/expression.h b/expression.h
new file mode 100644
index 0000000..36a0e02
--- /dev/null
+++ b/expression.h
@@ -0,0 +1,42 @@
+#ifndef LICHEN_EXPRESSION_H
+#define LICHEN_EXPRESSION_H
+
+/****************************************************************
+ * 
+ * a grammar is built on both nonterminals and terminals. both are
+ * represented by integers; nonterminals must be less than MAX_NONTERMINAL
+ * and terminals must be greater. the intended way to do this is to define
+ * an enum with all symbols, and have a MAX_NONTERMINAL symbol dividing the
+ * (low) nonterminals from the (high) terminals.
+ *
+ ****************************************************************
+ */
+
+struct li_production_t {
+  int *seq;
+  size_t seq_len;
+  struct li_production_t *next;  
+};
+
+struct li_production_t * li_production_alloc(size_t seq_len);
+void li_production_free(struct li_production_t *prod);
+
+struct li_production_rule_t {
+  size_t num_productions;
+  struct li_production_t *head;
+};
+
+struct li_production_rule_t * li_prod_rule_alloc();
+void li_prod_rule_free(struct li_production_rule_t *rule);
+int li_prod_rule_add(struct li_production_rule_t *rule, size_t seq_len, int *seq);
+
+typedef struct li_grammar_t {
+  struct li_production_rule_t *rules;
+  size_t num_nonterminal;
+} li_grammar_t;
+
+li_rammar_t * li_grammar_alloc(size_t num_nonterminal);
+void li_grammar_free(li_grammar_t *grammar);
+int li_grammar_rule_add(li_grammar_t *grammar, int nonterminal, size_t seq_len, int *seq);
+
+#endif