split up eval code

tokenize.l

@@ -51,7 +51,8 @@ enum yytokentype {
   QUOTE  = 264
 };
 
-struct token *make_token(enum yytokentype, int, char*);
+struct token* make_token(enum yytokentype, int, char*);
+struct ast*   eval(struct ast *a, struct env *e);
 int   yylval;
 char *yystr;
 %}
@@ -95,7 +96,8 @@ debug_token(struct token *x, int indent) {
 }
 
 void
-debug_ast(struct ast *a, int indent) {
+debug_ast(struct ast *a, int indent)
+{
   while (a) {
     for (int i = 0; i < indent; i++) putc(' ', stderr);
     fprintf(stderr, "AST: %s,a=%p,list=%p,token=%p,next=%p", (a->type == AST_TOK) ? "AST_TOK" :
@@ -155,6 +157,10 @@ make_env(char *name, struct ast *a)
    return e;
 }
 
+int token_is_num(struct token *t) {return t->type == NUM;}
+int token_is_sym(struct token *t) {return t->type == SYM;}
+int token_is_str(struct token *t) {return t->type == STR;}
+
 /* upon parsing a list of tokens like:
  *    "(" -> "def" -> "(" -> "b" -> ")" -> "c" -> ")"
  * care must be taken when entering a new sub-list (b),
@@ -224,68 +230,90 @@ lookup(struct env *e, char *name)
   return lookup(e->parent, name);
 }
 
+/* (def a <ausdruck>) */
+struct ast *
+eval_def(struct ast *a, struct env *e)
+{
+  a = a->next;                        /* skrip `def` */
+  assert((a->next->type == AST_TOK && 
+          a->next->v.token->type== STR)  ||
+         (a->next->type == AST_TOK && 
+          a->next->v.token->type == NUM) ||
+         (a->next->type == AST_LIST)     ||      
+         (a->next->type == AST_TOK && 
+          a->next->v.token->type== SYM));
+  
+  append(e, make_env(a->v.token->v.str, eval(a->next, e)));
+
+  assert(a->next->next == NULL);
+  return NULL;
+}
+
+/* (add <ausdruck::NUM> <audsruck::NUM> */
+struct ast *
+eval_add(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(NUM, 
+                             op1->v.token->v.num + 
+                             op2->v.token->v.num,
+                             NULL));
+}
+
+struct ast *
+eval_sym(struct ast *a, struct env *e)
+{
+  if (strcmp(a->v.token->v.str, "def") == 0)
+    return eval_def(a, e);
+  else if (strcmp(a->v.token->v.str, "lm") == 0) {
+  } else if (strcmp(a->v.token->v.str, "if") == 0) {
+  } else if (strcmp(a->v.token->v.str, "add") == 0) {
+    return eval_add(a, e);
+  } else if (strcmp(a->v.token->v.str, "q") == 0) {
+    //return make_ast(AST_QUOTE, a->next);
+    return a->next;
+  } else {
+    // fprintf(stderr, "Lookup: %s\n", a->v.token->v.str);
+    struct ast *var = lookup(e, a->v.token->v.str);
+    assert(var != NULL);            /* variable found? */
+    return var;
+  }
+  /* XXX: nand, eq, streq, symeq, add, sub, div, mul, 
+   *      mod, lt, numeq, num2bool
+   */
+  return NULL;
+}
+
 struct ast *
 eval(struct ast *a, struct env *e)
 {
   if (a == NULL) return NULL;
-
-  if (a->type == AST_TOK) {
-    if (a->v.token->type == NUM) {
+  
+  switch (a->type) {
+  case AST_TOK:
+    if (token_is_num(a->v.token))
       return make_ast(AST_TOK, a->v.token);
-    }
-    else if (a->v.token->type == SYM) {
-      fprintf(stderr, "process: %s\n", a->v.token->v.str);
-      if (strcmp(a->v.token->v.str, "def") == 0) {
-        a = a->next;
-        assert((a->next->type == AST_TOK && 
-                a->next->v.token->type== STR)  ||
-               (a->next->type == AST_TOK && 
-                a->next->v.token->type == NUM) ||
-               (a->next->type == AST_LIST)     ||      
-               (a->next->type == AST_TOK && 
-                a->next->v.token->type== SYM));
-        append(e, make_env(a->v.token->v.str, eval(a->next, e)));
-        return NULL;
-      } else if (strcmp(a->v.token->v.str, "lm") == 0) {
-      } else if (strcmp(a->v.token->v.str, "if") == 0) {
-      } else if (strcmp(a->v.token->v.str, "add") == 0) {
-        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(NUM, 
-                                   op1->v.token->v.num + 
-                                     op2->v.token->v.num,
-                                   NULL));
-      } else if (strcmp(a->v.token->v.str, "q") == 0) {
-        //return make_ast(AST_QUOTE, a->next);
-        return a->next;
-      } else {
-        // fprintf(stderr, "Lookup: %s\n", a->v.token->v.str);
-        struct ast *var = lookup(e, a->v.token->v.str);
-        assert(var != NULL);            /* variable found? */
-        return var;
-      }
-      /* XXX: nand, eq, streq, symeq, add, sub, div, mul, 
-       *      mod, lt, numeq, num2bool
-       */
-
-    } else if (a->v.token->type == STR)
+    else if (token_is_sym(a->v.token))
+      return eval_sym(a, e);
+    else if (token_is_str(a->v.token))
       return make_ast(AST_TOK, a->v.token);
-  } else if (a->type == AST_LIST) {
+  case AST_LIST:
     return eval(a->v.list, e);
-  } else {
+  default:
     fprintf(stderr, "%d\n", a->type);
     assert(0);
   }