make symbols and add nil

stage2/include/lisp.h

@@ -3,7 +3,7 @@
 
 #define     SYMBOL_TABLE_SIZE       2048
 
-typedef char *  symbol_t;
+typedef unsigned int  symbol_t;
 
 #define     TYPE_SYMBOL     1
 #define     TYPE_NUMBER     2
@@ -18,7 +18,6 @@ typedef char *  symbol_t;
 #define     floatp(x)       (x->type == TYPE_FLOAT)
 #define     listp(x)        (x->type == TYPE_LIST)
 
-
 typedef struct cell {
     uint8_t                 type;
     union {
@@ -35,5 +34,14 @@ typedef struct cell {
             };
         };
     };
-} cell_t;
+};
 
+
+symbol_t     intern_symbol(const char *s);
+symbol_t     make_symbol(const char *s);
+
+static auto NIL = make_symbol("nil");
+
+
+cell  head(cell x);
+cell  tail(cell x);

stage2/include/neopixel.h

@@ -3,6 +3,7 @@
 namespace neopxl {
 
 void        start();
-bool        blink(bool);
+void        blink();
+void        stop();
 
 } // namespace neopxl

stage2/platformio.ini

@@ -24,6 +24,7 @@ lib_deps =
     adafruit/RTClib @ ^1.12.4
     arduino-libraries/SD @ ^1.2.4
     arturo182/BBQ10Keyboard
+    kisom/kasl @ ^1.0.1
     SPI
     Wire
 

stage2/src/lisp.cc

@@ -1,5 +1,80 @@
 #include "lisp.h"
+#include "memory.h"
+#include "neopixel.h"
 
+#include <cstdlib>
+#include <cstring>
+
+#define MAX_SYMBOL_LEN  24
 
 static char      SymbolTable[SYMBOL_TABLE_SIZE];
+static cell      CellTable[SYMBOL_TABLE_SIZE]; // TODO(kyle): consider adding
+                                               // cell-table specific param.
+
+
+static void
+Abort()
+{
+    neopxl::stop();
+    abort();
+}
+
+
+symbol_t
+intern_symbol(const char *s)
+{
+    char    *cursor = SymbolTable;
+
+    if (!(std::strncmp(s, cursor+1, MAX_SYMBOL_LEN) == 0)) {
+        cursor += cursor[0];
+    }
+
+    // cursor has reached the end of the symbol table, which means
+    // we are out of room.
+    if (cursor >= SymbolTable+SYMBOL_TABLE_SIZE) {
+        Abort();
+    }
+
+    // cursor has reached the end of the symbol list, which means it
+    // should be added to the symbol table.
+    if (cursor[0] == 0) {
+        cursor[0] = static_cast<uint8_t>(strnlen(s, MAX_SYMBOL_LEN));
+        memcpy(cursor+1, s, static_cast<size_t>(cursor[0]));
+        cursor[cursor[0]+1] = 0;
+    }
+
+    // return the symbol pointed to by the cursor.
+    return (symbol_t)(cursor);
+}
+
+
+static cell *
+FindEmptyCell()
+{
+    auto cursor = CellTable;
+
+    while (cursor < (CellTable + SYMBOL_TABLE_SIZE)) {
+        if (cursor->type == 0) {
+            return cursor;
+        }
+    }
+
+    return nullptr;
+}
+
+
+
+symbol_t
+make_symbol(const char *s)
+{
+    cell  *cell = FindEmptyCell();
+    if (cell == nullptr) {
+        Abort();
+    }
+    
+    cell->type = TYPE_SYMBOL;
+    cell->sym = intern_symbol(s);
+
+    return cell->sym;
+}
 

stage2/src/main.cc

@@ -2,6 +2,8 @@
 #include <Adafruit_ILI9341.h>
 #include <Fonts/FreeSans12pt7b.h>
 
+#include <kasl/scheduling.h>
+
 #include "display.h"
 #include "neopixel.h"
 
@@ -13,7 +15,7 @@ setup()
 	Serial.begin(115200);
 
 	neopxl::start();
-	tft::Setup;
+	tft::Setup();
 	tft::SetCursor(0, 8);
 
   	
@@ -21,6 +23,9 @@ setup()
 	tft::Println(" \\ (square 3)");
 	tft::Println(" 9");
 	tft::Println(" \\ ");
+
+	kasl::scheduleThread(neopxl::blink);
+	kasl::startScheduler();
 }
 
 
@@ -29,6 +34,6 @@ loop()
 {
 	static bool	on = false;
 
-	on = neopxl::blink(on);
+	kasl::runScheduler();
 	delayMicroseconds(100);
 }

stage2/src/neopixel.cc

@@ -35,9 +35,15 @@ start()
 }
 
 
-bool
-blink(bool on)
+static bool	run = true;
+
+
+void
+blink()
 {
+	static bool		on = false;
+
+	while (run) {
 		if (on) {
 			for (int i = 10; i < 255; i++) {
 				auto c = pixels.Color(0, (uint8_t)i, 0);
@@ -45,7 +51,6 @@ blink(bool on)
 				pixels.show();
 				delay(4);
 			}
-		on = false;
 		} else {
 			for (int i = 255; i > 9; i--) {
 				auto c = pixels.Color(0, (uint8_t)i, 0);
@@ -53,12 +58,20 @@ blink(bool on)
 				pixels.show();
 				delay(4);
 			}
-		on = true;
 		}
 
-	return on;
+		on = !on;
+	}
 }
 
 
+void
+stop()
+{
+	run = false;
+	delay(980);
+	pixels.setPixelColor(0, cRed);
+	pixels.show();
+}
 
 }; // namespace neopxl