quick and easy semantic actions

5 files changed, 56 insertions, 12 deletions

diff --git a/clr-table.c b/clr-table.c
index 23345ec..fb68826 100644
--- a/clr-table.c
+++ b/clr-table.c
@@ -68,7 +68,7 @@ static void itemset_print(struct item *set, size_t nset)
 static size_t itemset_handle(struct item *set, size_t nset)
 {
 #ifdef _LAZY_LALR
-    int use_state = SIZE_MAX;
+    size_t use_state = SIZE_MAX;
 #endif
 
     // 1. is set in seen_sets
diff --git a/demos/generate-parser.c b/demos/generate-parser.c
index 8d50ad6..d32a697 100644
--- a/demos/generate-parser.c
+++ b/demos/generate-parser.c
@@ -14,6 +14,8 @@ int (*symbol_is_valid)(symbol s);
 struct production *grammar;
 size_t total_productions;
 
+char **semantic_action_str;
+
 #include "util-tables.c"
 
 #define _LAZY_LALR
@@ -35,19 +37,21 @@ void *xdlsym(void *handle, char *sym)
 int main(int argc, char **argv)
 {
     if(argc != 2) return 1;
-    
+
     void *handle = dlopen(argv[1], RTLD_LAZY);
     if(!handle) { puts(dlerror()); return 1; }
 
-    GET_VARIABLE(total_symbols, handle);    
+    GET_VARIABLE(total_symbols, handle);
     GET_VARIABLE(symbol_is_terminal, handle);
     GET_VARIABLE(symbol_is_input_end, handle);
     GET_VARIABLE(symbol_is_valid, handle);
     GET_VARIABLE(grammar, handle);
     GET_VARIABLE(total_productions, handle);
+    GET_VARIABLE(semantic_action_str, handle);
+
     util_tables_fill();
     table_fill() && (fprintf(stderr, "ERROR: Table couldn't be generated\n"), exit(1), 1);
-    
+
     printf("size_t total_symbols = %zu;\n", total_symbols);
     printf("IMPLEMENT_FUNCPTR(int, symbol_is_valid, (symbol s), {return s < total_symbols;})\n");
 
@@ -57,15 +61,32 @@ int main(int argc, char **argv)
 
     printf("struct production *grammar = _grammar;");
     printf("size_t total_productions = %zu;\n", total_productions);
-    
-    printf("struct action **table = (struct action *([])){\n", table_states, total_symbols);
+
+    printf("struct action **table = (struct action *([])){\n");
     table_print_cstyle();
     printf("};\n");
     printf("size_t table_states = %zu;\n", table_states);
 
+    for(size_t i = 0; i < total_productions; i++) {
+        printf("#define A(n) (*(stack_head-3*%d+3*n-1))\n", grammar[i].nRHS-1);
+        printf("int __prod%d_action(int *stack_head)\n", i);
+        printf("{ int v;\n");
+        printf(semantic_action_str[i]);
+        printf("return v; }\n");
+        printf("#undef A\n");
+    }
+
+
+    printf("typedef int (*semantic_action_fn)(int *stack_head);\n");
+
+    printf("semantic_action_fn *semantic_actions = (semantic_action_fn[]){\n");
+    for(size_t i = 0; i < total_productions; i++)
+        printf("__prod%d_action, ", i);
+    printf("};");
+
     table_free();
     util_tables_free();
-    
+
     dlclose(handle);
     return 0;
 }
diff --git a/demos/sample-files/defs.c b/demos/sample-files/defs.c
index 92d6837..76a0534 100644
--- a/demos/sample-files/defs.c
+++ b/demos/sample-files/defs.c
@@ -35,3 +35,15 @@ static struct production _grammar[] = {
 
 struct production *grammar = _grammar;
 size_t total_productions = sizeof(_grammar)/sizeof(*_grammar);
+
+// #include "???.h"
+char **semantic_action_str = (char *([])){
+    "v = A(0);",
+    "v = A(0) + A(2);",
+    "v = A(0) - A(2);",
+    "v = A(0);",
+    "v = A(1);",
+    "v = A(0);",
+    "v = 0;",
+    "v = 1;",
+};
diff --git a/demos/sample-files/parser-skeleton.c b/demos/sample-files/parser-skeleton.c
index 031d829..f601369 100644
--- a/demos/sample-files/parser-skeleton.c
+++ b/demos/sample-files/parser-skeleton.c
@@ -41,10 +41,12 @@ int main(int argc, char **argv)
 {
     if(argc != 2) {
         fprintf(stderr, "ERROR: Not enough arguments\n");
-        return 1;   
+        return 1;
     }
 
     input = argv[1];
-    
-    return lr_parser();
+
+    printf("INPUT: '%s'\n", input);
+    printf("OUTPUT: %d\n", lr_parser());
+    return 0;
 }
diff --git a/lr-parser.c b/lr-parser.c
index 3ab9af4..f7197c5 100644
--- a/lr-parser.c
+++ b/lr-parser.c
@@ -9,6 +9,9 @@
 #include "parts/grammar.h"
 #include "parts/table.h"
 #include "parts/toklist.h"
+// and
+typedef int (*semantic_action_fn)(int *stack_head);
+extern semantic_action_fn *semantic_actions;
 
 typedef int stack_item;
 
@@ -32,10 +35,12 @@ int lr_parser()
         switch(a.type) {
         case ACTION_SHIFT:
             push(eat());
+            push(-10000000); // the semantic action
             push(a.arg);
             break;
         case ACTION_REDUCE:
-            for(size_t i = 0; i < 2*grammar[a.arg].nRHS; i++) pop();
+            int semantic_value = semantic_actions[a.arg](stack_head);
+            for(size_t i = 0; i < 3*grammar[a.arg].nRHS; i++) pop();
 
             symbol lhs = grammar[a.arg].LHS;
             struct action a_goto = table[(size_t)*stack_head][lhs];
@@ -47,10 +52,11 @@ int lr_parser()
             }
 
             push(lhs);
+            push(semantic_value);
             push(a_goto.arg);
             break;
         case ACTION_ACCEPT:
-            return 0;
+            return *(stack_head-1);
         case ACTION_NOT_SET:
         default:
             fprintf(stderr,
@@ -124,6 +130,9 @@ static symbol *tok = toklist;
 symbol toklist_eat() { return *(tok++); } // unsafe
 symbol toklist_peek() { return *tok; }    // unsafe
 
+int none(int *stack_head) {(void)stack_head; return 0;};
+semantic_action_fn *semantic_actions = (semantic_action_fn[]){none, none, none, none, none, none, none, none};
+
 int main(void)
 {
     return lr_parser();