diff --git a/ulisp/platformio.ini b/ulisp/platformio.ini
index 50208f0..ec41326 100644
--- a/ulisp/platformio.ini
+++ b/ulisp/platformio.ini
@@ -12,3 +12,4 @@
 platform = atmelsam
 board = adafruit_feather_m4
 framework = arduino
+lib_deps = arduino-libraries/SD
diff --git a/ulisp/src/ulisp.cc b/ulisp/src/ulisp.cc
index 71e643c..a9cd616 100644
--- a/ulisp/src/ulisp.cc
+++ b/ulisp/src/ulisp.cc
@@ -14,7 +14,7 @@ const char LispLibrary[] PROGMEM = "";
 // #define resetautorun
 #define printfreespace
 // #define printgcs
-// #define sdcardsupport
+#define sdcardsupport
 // #define gfxsupport
 // #define lisplibrary
 #define assemblerlist
@@ -183,7 +183,7 @@ typedef int PinMode;
   #define CPU_ATSAMD21
 
 #elif defined(ARDUINO_METRO_M4) || defined(ARDUINO_ITSYBITSY_M4) || defined(ARDUINO_FEATHER_M4) || defined(ARDUINO_PYBADGE_M4) || defined(ARDUINO_PYGAMER_M4)
-  #define WORKSPACESIZE 20480-SDSIZE      /* Objects (8*bytes) */
+  #define WORKSPACESIZE (20480-SDSIZE)      /* Objects (8*bytes) */
   #define DATAFLASHSIZE 2048000           /* 2 MBytes */
   #define SYMBOLTABLESIZE 1024            /* Bytes */
   #define CODESIZE 256                    /* Bytes */
@@ -309,16 +309,55 @@ enum flag { PRINTREADABLY, RETURNFLAG, ESCAPE, EXITEDITOR, LIBRARYLOADED, NOESC
 volatile char Flags = 0b00001; // PRINTREADABLY set by default
 
 // Forward references
+bool consp (object *x);
+bool atom (object *x);
+bool listp (object *x);
+bool improperp (object *x);
+object *quote (object *arg);
 object *tee;
 object *tf_progn (object *form, object *env);
 object *eval (object *form, object *env);
-object *read (gfun_t gfun);
-void repl (object *env);
+object *read (pfun_t pfun);
+void repl(object *env);
 void printobject (object *form, pfun_t pfun);
 char *lookupbuiltin (symbol_t name);
-intptr_t lookupfn (symbol_t name);
+int lookupfn (symbol_t name);
+int lookupmin(symbol_t name);
+int lookupmax(symbol_t name);
 int builtin (char* n);
-
+void Display (char c);
+void error (const __FlashStringHelper *);
+void pfstring (const char *s, pfun_t pfun);
+void pfstring (const __FlashStringHelper *);
+void pln (pfun_t pfun);
+void pfl (pfun_t pfun);
+void pchar (char c);
+int gchar ();
+object *apply (object *function, object *args, object **env);
+char *lookupsymbol (symbol_t name);
+void deletesymbol (symbol_t name);
+object *edit(object *fun);
+int subwidthlist (object *form, int w);
+void superprint (object *form, int lm);
+void supersub (object *form, int lm, int super, pfun_t pfun);
+void pserial (char c);
+char *symbolname (symbol_t x);
+void pstring (char *s, pfun_t pfun);
+int maxbuffer (char *buffer);
+char nthchar (object *string, int n);
+object *apply (symbol_t name, object *function, object *args, object *env);
+int listlength (symbol_t name, object *list);
+void checkminmax (symbol_t name, int nargs);
+void pint (int i, pfun_t pfun);
+void testescape ();
+int gserial ();
+void pinthex (uint32_t i, pfun_t pfun);
+void printhex4 (int i, pfun_t pfun);
+void prin1object (object *form, pfun_t pfun);
+int assemble (int pass, int origin, object *entries, object *env, object *pcpair);
+void printstring (object *form, pfun_t pfun);
+int glibrary ();
+ 
 // Error handling
 
 void errorsub (symbol_t fname, PGM_P string) {
@@ -902,7 +941,9 @@ object *quote (object *arg) {
 int toradix40 (char ch) {
   if (ch == 0) return 0;
   if (ch >= '0' && ch <= '9') return ch-'0'+30;
-  if (ch == '$') return 27; if (ch == '*') return 28; if (ch == '-') return 29;
+  if (ch == '$') return 27;
+  if (ch == '*') return 28;
+  if (ch == '-') return 29;
   ch = ch | 0x20;
   if (ch >= 'a' && ch <= 'z') return ch-'a'+1;
   return -1; // Invalid
@@ -910,7 +951,9 @@ int toradix40 (char ch) {
 
 int fromradix40 (int n) {
   if (n >= 1 && n <= 26) return 'a'+n-1;
-  if (n == 27) return '$'; if (n == 28) return '*'; if (n == 29) return '-';
+  if (n == 27) return '$';
+  if (n == 28) return '*';
+  if (n == 29) return '-';
   if (n >= 30 && n <= 39) return '0'+n-30;
   return 0;
 }
@@ -3623,7 +3666,7 @@ object *fn_readfromstring (object *args, object *env) {
   if (!stringp(arg)) error(READFROMSTRING, notastring, arg);
   GlobalString = arg;
   GlobalStringIndex = 0;
-  return read(gstr);
+  return read((pfun_t)gstr);
 }
 
 object *fn_princtostring (object *args, object *env) {   
@@ -3734,7 +3777,7 @@ object *fn_break (object *args, object *env) {
 object *fn_read (object *args, object *env) {
   (void) env;
   gfun_t gfun = gstreamfun(args);
-  return read(gfun);
+  return read((pfun_t)gfun);
 }
 
 object *fn_prin1 (object *args, object *env) {
@@ -3964,9 +4007,9 @@ object *edit (object *fun) {
     char c = gserial();
     if (c == 'q') setflag(EXITEDITOR);
     else if (c == 'b') return fun;
-    else if (c == 'r') fun = read(gserial);
+    else if (c == 'r') fun = read((pfun_t)gserial);
     else if (c == '\n') { pfl(pserial); superprint(fun, 0, pserial); pln(pserial); }
-    else if (c == 'c') fun = cons(read(gserial), fun);
+    else if (c == 'c') fun = cons(read((pfun_t)gserial), fun);
     else if (atom(fun)) pserial('!');
     else if (c == 'd') fun = cons(car(fun), edit(cdr(fun)));
     else if (c == 'a') fun = cons(edit(car(fun)), cdr(fun));
@@ -4112,7 +4155,7 @@ object *fn_require (object *args, object *env) {
     globals = cdr(globals);
   }
   GlobalStringIndex = 0;
-  object *line = read(glibrary);
+  object *line = read((pfun_t)glibrary);
   while (line != NULL) {
     // Is this the definition we want
     int fname = first(line)->name;
@@ -4120,7 +4163,7 @@ object *fn_require (object *args, object *env) {
       eval(line, env);
       return tee;
     }
-    line = read(glibrary);
+    line = read((pfun_t)glibrary);
   }
   return nil; 
 }
@@ -4128,13 +4171,13 @@ object *fn_require (object *args, object *env) {
 object *fn_listlibrary (object *args, object *env) {
   (void) args, (void) env;
   GlobalStringIndex = 0;
-  object *line = read(glibrary);
+  object *line = read((pfun_t)glibrary);
   while (line != NULL) {
     int fname = first(line)->name;
     if (fname == DEFUN || fname == DEFVAR) {
       pstring(symbolname(second(line)->name), pserial); pserial(' ');
     }
-    line = read(glibrary);
+    line = read((pfun_t)glibrary);
   }
   return symbol(NOTHING); 
 }
@@ -5193,10 +5236,10 @@ int glibrary () {
 
 void loadfromlibrary (object *env) {   
   GlobalStringIndex = 0;
-  object *line = read(glibrary);
+  object *line = read((pfun_t)glibrary);
   while (line != NULL) {
     eval(line, env);
-    line = read(glibrary);
+    line = read((pfun_t)glibrary);
   }
 }
 
@@ -5370,13 +5413,13 @@ object *nextitem (gfun_t gfun) {
     else if (ch == '\'') return nextitem(gfun);
     else if (ch == '.') {
       setflag(NOESC);
-      object *result = eval(read(gfun), NULL);
+      object *result = eval(read((pfun_t)gfun), NULL);
       clrflag(NOESC);
       return result;
     }
-    else if (ch == '(') { LastChar = ch; return readarray(1, read(gfun)); }
-    else if (ch == '*') return readbitarray(gfun);
-    else if (ch >= '1' && ch <= '9' && (gfun() & ~0x20) == 'A') return readarray(ch - '0', read(gfun));
+    else if (ch == '(') { LastChar = ch; return readarray(1, read((pfun_t)gfun)); }
+    else if (ch == '*') return readbitarray((gfun_t)gfun);
+    else if (ch >= '1' && ch <= '9' && (gfun() & ~0x20) == 'A') return readarray(ch - '0', read((pfun_t)gfun));
     else error2(0, PSTR("illegal character after #"));
     ch = gfun();
   }
@@ -5447,9 +5490,9 @@ object *readrest (gfun_t gfun) {
     if (item == (object *)BRA) {
       item = readrest(gfun);
     } else if (item == (object *)QUO) {
-      item = cons(symbol(QUOTE), cons(read(gfun), NULL));
+      item = cons(symbol(QUOTE), cons(read((pfun_t)gfun), NULL));
     } else if (item == (object *)DOT) {
-      tail->cdr = read(gfun);
+      tail->cdr = read((pfun_t)gfun);
       if (readrest(gfun) != NULL) error2(0, PSTR("malformed list"));
       return head;
     } else {