Add COLOR= and PLOT.

main.c

@@ -47,6 +47,8 @@ uint8_t title_length = 9;
 #define T_THEN 0x92
 #define T_GR 0x93
 #define T_TEXT 0x94
+#define T_COLOR 0x95
+#define T_PLOT 0x96
 
 // Operators. These encode both the operator (high nybble) and the precedence
 // (low nybble). Lower precedence has a lower low nybble value. For example,
@@ -117,6 +119,8 @@ static uint8_t *TOKEN[] = {
     "THEN",
     "GR",
     "TEXT",
+    "COLOR",
+    "PLOT",
 };
 static int16_t TOKEN_COUNT = sizeof(TOKEN)/sizeof(TOKEN[0]);
 
@@ -771,6 +775,26 @@ static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
         } else if (*s == T_TEXT) {
             s += 1;
             add_call(text_statement);
+        } else if (*s == T_COLOR) {
+            s += 1;
+            if (*s != T_EQUAL) {
+                error = 1;
+            } else {
+                s += 1;
+                s = compile_expression(s);
+                add_call(color_statement);
+            }
+        } else if (*s == T_PLOT) {
+            s += 1;
+            s = compile_expression(s);
+            add_call(pushax);
+            if (*s != ',') {
+                error = 1;
+            } else {
+                s += 1;
+                s = compile_expression(s);
+                add_call(plot_statement);
+            }
         } else {
             error = 1;
         }
@@ -980,6 +1004,7 @@ int16_t main(void)
 {
     int16_t blink;
 
+    /*
        // For testing generated code. TODO remove
     {
         int16_t a, b, c;
@@ -987,6 +1012,7 @@ int16_t main(void)
         c = 6;
         a = b == c;
     }
+    */
 
     // Clear stored program.
     new_statement();

runtime.c

@@ -21,6 +21,10 @@ uint8_t g_cursor_ch = 0;
 // Whether in low-res graphics mode.
 uint8_t g_gr_mode = 0;
 
+// 4-bit low-res color.
+uint8_t g_gr_color_high = 0; // High nybble.
+uint8_t g_gr_color_low = 0;  // Low nybble.
+
 // List of variable names, two bytes each, in the same order they are
 // in the zero page (starting at FIRST_VARIABLE). Two nuls means an unused
 // slot. One-letter variable names have a nul for the second character.
@@ -250,3 +254,26 @@ void text_statement(void) {
 
     g_gr_mode = 0;
 }
+
+/**
+ * Set the low-res color.
+ */
+void color_statement(uint16_t color) {
+    g_gr_color_high = (uint8_t) ((color << 4) & 0xF0);
+    g_gr_color_low = (uint8_t) (color & 0x0F);
+}
+
+/**
+ * Plot a pixel in low-res graphics mode.
+ */
+void plot_statement(uint16_t x, uint16_t y) {
+    uint8_t *pos = screen_pos(x, y >> 1);
+
+    if ((y & 1) == 0) {
+        // Even, bottom pixel.
+        *pos = (*pos & 0xF0) | g_gr_color_low;
+    } else {
+        // Odd, top pixel.
+        *pos = (*pos & 0x0F) | g_gr_color_high;
+    }
+}

runtime.h

@@ -38,5 +38,7 @@ void syntax_error_in_line(uint16_t line_number);
 
 void gr_statement(void);
 void text_statement(void);
+void color_statement(uint16_t color);
+void plot_statement(uint16_t x, uint16_t y);
 
 #endif // __RUNTIME_H__