feat: add modular Forth interpreter implementation

Co-authored-by: aider (openrouter/tencent/hy3-preview:free) <aider@aider.chat>

forth_core.c

@@ -0,0 +1,103 @@
+#include "forth.h"
+
+// Global variables
+int32_t data_stack[DATA_STACK_SIZE];
+int sp = -1;
+Cell ret_stack[RET_STACK_SIZE];
+int rp = -1;
+Cell* ip = NULL;
+
+Word dict[DICT_SIZE];
+int dict_idx = 0;
+Word* dict_head = NULL;
+Cell dict_bodies[BODY_SIZE];
+int body_idx = 0;
+
+int state = 0;
+Cell compile_buf[COMPILE_BUF_SIZE];
+int compile_idx = 0;
+char compiling_name[MAX_NAME_LEN + 1];
+
+char input_buf[INPUT_BUF_SIZE];
+char* input_ptr = NULL;
+
+Cell* compile_stack[COMPILE_STACK_SIZE];
+int compile_sp = -1;
+
+int32_t user_mem[USER_MEMORY_SIZE];
+int32_t* here = &user_mem[0];
+
+// Stack helpers
+void data_push(int32_t val) {
+    if (sp < DATA_STACK_SIZE - 1) {
+        data_stack[++sp] = val;
+    } else {
+        printf("Data stack overflow\n");
+    }
+}
+
+int32_t data_pop(void) {
+    if (sp >= 0) {
+        return data_stack[sp--];
+    } else {
+        printf("Data stack underflow\n");
+        return 0;
+    }
+}
+
+void ret_push_ip(Cell* val) {
+    if (rp < RET_STACK_SIZE - 1) {
+        rp++;
+        ret_stack[rp].cell_ptr = val;
+    } else {
+        printf("Return stack overflow\n");
+    }
+}
+
+Cell* ret_pop_ip(void) {
+    if (rp >= 0) {
+        Cell* res = ret_stack[rp].cell_ptr;
+        rp--;
+        return res;
+    } else {
+        printf("Return stack underflow\n");
+        return NULL;
+    }
+}
+
+void ret_push_num(int32_t val) {
+    if (rp < RET_STACK_SIZE - 1) {
+        rp++;
+        ret_stack[rp].num = val;
+    } else {
+        printf("Return stack overflow\n");
+    }
+}
+
+int32_t ret_pop_num(void) {
+    if (rp >= 0) {
+        int32_t res = ret_stack[rp].num;
+        rp--;
+        return res;
+    } else {
+        printf("Return stack underflow\n");
+        return 0;
+    }
+}
+
+void compile_push(Cell* addr) {
+    if (compile_sp < COMPILE_STACK_SIZE - 1) {
+        compile_stack[++compile_sp] = addr;
+    } else {
+        printf("Compile stack overflow\n");
+    }
+}
+
+Cell* compile_pop(void) {
+    if (compile_sp >= 0) {
+        return compile_stack[compile_sp--];
+    } else {
+        printf("Compile stack underflow\n");
+        return NULL;
+    }
+}