From e718421f1712ae5172d4ed855a40ec761695febc Mon Sep 17 00:00:00 2001
From: Christian Barthel <bch@online.de>
Date: Sun, 30 Jun 2019 22:44:14 +0200
Subject: [PATCH] lower than

---
 tokenize.l | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tokenize.l b/tokenize.l
index 0e23c61..af83d0c 100644
--- a/tokenize.l
+++ b/tokenize.l
@@ -306,6 +306,31 @@ eval_add(struct ast *a, struct env *e)
                              NULL));
 }
 
+/* (lt <ausdruck::NUM> <audsruck::NUM>) -> BOOL*/
+struct ast *
+eval_lt(struct ast *a, struct env *e)
+{
+  assert (a != NULL && 
+          a->next != NULL &&
+          a->next->next != NULL &&
+          a->next->next->next == NULL);
+
+  struct ast *op1 = eval(a->next, e);
+  struct ast *op2 = eval(a->next->next, e);
+        
+  assert (op1 != NULL &&
+          op1->type == AST_TOK &&
+          op1->v.token->type == NUM &&
+          op2 != NULL &&
+          op2->type == AST_TOK &&
+          op2->v.token->type == NUM);
+  return make_ast(AST_TOK, 
+                  make_token(BOOL, 
+                             op1->v.token->v.num <
+                             op2->v.token->v.num,
+                             NULL));
+}
+
 /* (inv <ausdruck::NUM>) -> NUM */
 struct ast *
 eval_inv(struct ast *a, struct env *e)
@@ -336,6 +361,8 @@ eval_sym(struct ast *a, struct env *e)
     return eval_inv(a, e);
   } else if (strcmp(a->v.token->v.str, "add") == 0) {
     return eval_add(a, e);
+  } else if (strcmp(a->v.token->v.str, "lt") == 0) {
+    return eval_lt(a, e);
   } else if (strcmp(a->v.token->v.str, "nand") == 0) {
     return eval_nand(a, e);
   } else if (strcmp(a->v.token->v.str, "q") == 0) {