Added cosmoV_pushFString(), and cosmoO_pushVFString().

cosmoV_error now pushes the error string onto the stack, as well as uses cosmoO_VFString to format strings.
cosmoV_concat is now entirely self contained, and is now stack based. Push the CValues you want to concat into strings onto the stack and call cosmoV_concat with the # of values you pushed.

src/cobj.c

@@ -224,6 +224,46 @@ CObjString *cosmoO_allocateString(CState *state, const char *str, size_t sz, uin
     return strObj;
 }
 
+CObjString *cosmoO_pushVFString(CState *state, const char *format, va_list args) {
+    StkPtr start = state->top;
+
+    while (true) {
+        const char *end = strchr(format, '%'); // grab the next occurrence of '%'
+        if (end == NULL) // the end, no '%' found
+            break;
+
+        // push the string before '%'
+        cosmoV_pushLString(state, format, (end - format));
+        char c = *(end+1); // the character right after '%'
+
+        switch (c) {
+            case 'd': { // int
+                cosmoV_pushNumber(state, va_arg(args, int));
+                break;
+            }
+            case 'f': { // double
+                cosmoV_pushNumber(state, va_arg(args, double));
+                break;
+            }
+            case 's': { // const char *
+                cosmoV_pushString(state, va_arg(args, char *));
+                break;
+            }
+            default: {
+                char temp[2];
+                temp[0] = '%';
+                temp[1] = c;
+                cosmoV_pushLString(state, temp, 2);
+            }
+        }
+        format = end + 2; // + 2 because of % and the following character
+    }
+
+    cosmoV_pushString(state, format); // push the rest of the string
+    cosmoV_concat(state, state->top - start); // use cosmoV_concat to concat all the strings on the stack
+    return cosmoV_readString(*start); // start should be state->top - 1
+}
+
 bool cosmoO_getObject(CState *state, CObjObject *object, CValue key, CValue *val) {
     if (!cosmoT_get(&object->tbl, key, val)) { // if the field doesn't exist in the object, check the proto
         if (cosmoO_getIString(state, object, ISTRING_GETTER, val) && IS_OBJECT(*val) && cosmoO_getObject(state, cosmoV_readObject(*val), key, val)) {

src/cobj.h

@@ -154,6 +154,15 @@ CObjString *cosmoO_takeString(CState *state, char *str, size_t sz);
 // allocates a CObjStruct pointing directly to *str
 CObjString *cosmoO_allocateString(CState *state, const char *str, size_t sz, uint32_t hash);
 
+/*
+    formats strings to push onto the VM stack, formatting supported:
+
+    '%d' - decimal numbers  [int]
+    '%f' - floating point   [double]
+    '%s' - strings          [const char*]
+*/
+CObjString *cosmoO_pushVFString(CState *state, const char *format, va_list args);
+
 COSMO_API void printObject(CObj *o);
 const char *cosmoO_typeStr(CObj* obj);
 

src/cvm.c

@@ -6,6 +6,13 @@
 #include <stdarg.h>
 #include <string.h>
 
+COSMO_API void cosmoV_pushFString(CState *state, const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    cosmoO_pushVFString(state, format, args);
+    va_end(args);
+}
+
 void cosmoV_error(CState *state, const char *format, ...) {
     if (state->panic)
         return;
@@ -37,14 +44,12 @@ void cosmoV_error(CState *state, const char *format, ...) {
 
     va_list args;
     va_start(args, format);
-    vfprintf(stderr, format, args);
+    CObjString *errString = cosmoO_pushVFString(state, format, args);
     va_end(args);
-    fputs("\n", stderr);
-    
-    // TODO: push error onto the stack :P
-    state->panic = true;
 
+    printf("%.*s\n", errString->length, errString->str);
     cosmoV_printStack(state);
+    state->panic = true;
 }
 
 CObjUpval *captureUpvalue(CState *state, CValue *local) {
@@ -97,15 +102,30 @@ void popCallFrame(CState *state, int offset) {
     state->frameCount--;
 }
 
-CObjString *cosmoV_concat(CState *state, CObjString *strA, CObjString *strB) {
+void cosmoV_concat(CState *state, int vals) {
-    size_t sz = strA->length + strB->length;
+    StkPtr start = state->top - vals;
-    char *buf = cosmoM_xmalloc(state, sz + 1); // +1 for null terminator
+    StkPtr end = cosmoV_getTop(state, 0);
 
-    memcpy(buf, strA->str, strA->length);
+    CObjString *result = cosmoV_toString(state, *start);
-    memcpy(buf + strA->length, strB->str, strB->length);
+    for (StkPtr current = start + 1; current <= end; current++) {
-    buf[sz] = '\0';
+        cosmoV_pushValue(state, cosmoV_newObj(result)); // so our GC can find our current result string
+        CObjString *otherStr = cosmoV_toString(state, *current);
+        cosmoV_pushValue(state, cosmoV_newObj(otherStr)); // also so our GC won't free otherStr
 
-    return cosmoO_takeString(state, buf, sz);
+        // concat the two strings together
+        size_t sz = result->length + otherStr->length;
+        char *buf = cosmoM_xmalloc(state, sz + 1); // +1 for null terminator
+        
+        memcpy(buf, result->str, result->length);
+        memcpy(buf + result->length, otherStr->str, otherStr->length);
+        buf[sz] = '\0';
+        result = cosmoO_takeString(state, buf, sz);
+
+        cosmoV_setTop(state, 2); // pop result & otherStr off the stack
+    }
+
+    state->top = start;
+    cosmoV_pushValue(state, cosmoV_newObj(result));
 }
 
 int cosmoV_execute(CState *state);
@@ -726,21 +746,7 @@ int cosmoV_execute(CState *state) {
             }
             case OP_CONCAT: {
                 uint8_t vals = READBYTE();
-                StkPtr start = state->top - vals;
+                cosmoV_concat(state, vals);
-                StkPtr end = cosmoV_getTop(state, 0);
-
-                CObjString *result = cosmoV_toString(state, *start);
-                for (StkPtr current = start + 1; current <= end; current++) {
-                    cosmoV_pushValue(state, cosmoV_newObj(result)); // so our GC can find our current result string
-                    CObjString *otherStr = cosmoV_toString(state, *current);
-                    cosmoV_pushValue(state, cosmoV_newObj(otherStr)); // also so our GC won't free otherStr
-                    result = cosmoV_concat(state, result, otherStr);
-
-                    cosmoV_setTop(state, 2); // pop result & otherStr off the stack
-                }
-
-                state->top = start;
-                cosmoV_pushValue(state, cosmoV_newObj(result));
                 break;
             }
             case OP_INCLOCAL: { // this leaves the value on the stack

src/cvm.h

@@ -17,6 +17,8 @@ COSMO_API COSMOVMRESULT cosmoV_call(CState *state, int args, int nresults);
 COSMO_API void cosmoV_makeObject(CState *state, int pairs);
 COSMO_API void cosmoV_makeDictionary(CState *state, int pairs);
 COSMO_API bool cosmoV_getObject(CState *state, CObjObject *object, CValue key, CValue *val);
+COSMO_API void cosmoV_concat(CState *state, int vals);
+COSMO_API void cosmoV_pushFString(CState *state, const char *format, ...);
 COSMO_API void cosmoV_error(CState *state, const char *format, ...);
 
 // nice to have wrappers

src/main.c

@@ -52,6 +52,7 @@ static void repl() {
     cosmoB_loadLibrary(state);
     cosmoB_loadDebug(state);
 
+    // add our custom REPL functions
     cosmoV_pushString(state, "quit");
     cosmoV_pushCFunction(state, cosmoB_quitRepl);
 
@@ -111,6 +112,12 @@ static void runFile(const char* fileName) {
     CState *state = cosmoV_newState();
     cosmoB_loadLibrary(state);
 
+    // add our input() function to the global table
+    cosmoV_pushString(state, "input");
+    cosmoV_pushCFunction(state, cosmoB_input);
+
+    cosmoV_register(state, 1);
+
     interpret(state, script, fileName);
 
     cosmoV_freeState(state);