OK, my idea that long multiplication is like long addition is wrong.

It's still broken, but it's broken because of fundamental misunderstanding which tinkering won't solve.

lisp/scratchpad.lisp

@@ -45,4 +45,4 @@
 (inspect (set! z (+ y y y y y y y y y y)))
 
 "This blows up: 10^37, which is a three cell bignum."
-(inspect (+ z z z z z z z z z z))
+(inspect (set! final (+ z z z z z z z z z z)))

lisp/scratchpad2.lisp

@@ -81,4 +81,5 @@
 (inspect
  (set! z (+ y y y y y y y y)))
 
-(inspect (+ z z z z z z z z))
+(inspect
+ (set! final (+ z z z z z z z z)))

src/arith/integer.c

@@ -27,6 +27,7 @@
 #include "conspage.h"
 #include "consspaceobject.h"
 #include "debug.h"
+#include "lispops.h"
 
 /*
  * The maximum value we will allow in an integer cell.
@@ -104,14 +105,20 @@ struct cons_pointer make_integer( int64_t value, struct cons_pointer more ) {
  * \see operate_on_integers
  */
 __int128_t cell_value( struct cons_pointer c, char op, bool is_first_cell ) {
-    long int val = nilp( c ) ? 0 : pointer2cell( c ).payload.integer.value;
+    long int val = nilp( c ) ?
+      0 :
+      pointer2cell( c ).payload.integer.value;
+
     long int carry = is_first_cell ? 0 : ( MAX_INTEGER + 1 );
 
     __int128_t result = ( __int128_t ) integerp( c ) ?
-        ( val == 0 ) ? carry : val : op == '*' ? 1 : 0;
+        ( val == 0 ) ?
+          carry :
+          val :
+         0;
     debug_printf( DEBUG_ARITH,
-                  L"cell_value: raw value is %ld, op = '%c', is_first_cell = %s; returning ",
+                  L"cell_value: raw value is %ld, op = '%c', is_first_cell = %s; %4.4s; returning ",
-                  val, op, is_first_cell ? "true" : "false" );
+                  val, op, is_first_cell ? "true" : "false", pointer2cell(c).tag.bytes);
     debug_print_128bit( result, DEBUG_ARITH );
     debug_println( DEBUG_ARITH );
 
@@ -139,6 +146,7 @@ struct cons_pointer operate_on_integers( struct cons_pointer a,
                                          struct cons_pointer b, char op ) {
     struct cons_pointer result = NIL;
     struct cons_pointer cursor = NIL;
+
     __int128_t carry = 0;
     bool is_first_cell = true;
 
@@ -163,7 +171,7 @@ struct cons_pointer operate_on_integers( struct cons_pointer a,
 
             switch ( op ) {
                 case '*':
-                    rv = av * ( bv + carry );
+                    rv = (av * bv) + carry;
                     break;
                 case '+':
                     rv = av + bv + carry;

src/ops/lispops.c

@@ -136,7 +136,12 @@ struct cons_pointer eval_forms( struct stack_frame *frame,
 /**
  * Return the object list (root namespace).
  *
- * (oblist)
+ * * (oblist)
+ *
+ * @param frame the stack frame in which the expression is to be interpreted;
+ * @param frame_pointer a pointer to my stack_frame.
+ * @param env my environment (ignored).
+ * @return the root namespace.
  */
 struct cons_pointer
 lisp_oblist( struct stack_frame *frame, struct cons_pointer frame_pointer,
@@ -165,12 +170,15 @@ struct cons_pointer compose_body( struct stack_frame *frame ) {
 }
 
 /**
- * Construct an interpretable function.
+ * Construct an interpretable function. *NOTE* that if `args` is a single symbol
+ * rather than a list, a varargs function will be created.
  *
  * (lambda args body)
  *
  * @param frame the stack frame in which the expression is to be interpreted;
+ * @param frame_pointer a pointer to my stack_frame.
  * @param env the environment in which it is to be intepreted.
+ * @return an interpretable function with these `args` and this `body`.
  */
 struct cons_pointer
 lisp_lambda( struct stack_frame *frame, struct cons_pointer frame_pointer,
@@ -179,12 +187,15 @@ lisp_lambda( struct stack_frame *frame, struct cons_pointer frame_pointer,
 }
 
 /**
- * Construct an interpretable special form.
+ * Construct an interpretable special form. *NOTE* that if `args` is a single symbol
+ * rather than a list, a varargs special form will be created.
  *
  * (nlambda args body)
  *
  * @param frame the stack frame in which the expression is to be interpreted;
+ * @param frame_pointer a pointer to my stack_frame.
  * @param env the environment in which it is to be intepreted.
+ * @return an interpretable special form with these `args` and this `body`.
  */
 struct cons_pointer
 lisp_nlambda( struct stack_frame *frame, struct cons_pointer frame_pointer,
@@ -612,6 +623,16 @@ lisp_set_shriek( struct stack_frame *frame, struct cons_pointer frame_pointer,
     return result;
 }
 
+/**
+ * @return true if `arg` represents an end of string, else false.
+ * \todo candidate for moving to a memory/string.c file
+ */
+bool end_of_stringp(struct cons_pointer arg) {
+  return nilp(arg) ||
+    ( stringp( arg ) &&
+     pointer2cell(arg).payload.string.character == (wint_t)'\0');
+}
+
 /**
  * Function;
  * returns a cell constructed from a and b. If a is of type string but its
@@ -634,7 +655,8 @@ lisp_cons( struct stack_frame *frame, struct cons_pointer frame_pointer,
 
     if ( nilp( car ) && nilp( cdr ) ) {
         return NIL;
-    } else if ( stringp( car ) && stringp( cdr )) {
+    } else if ( stringp( car ) && stringp( cdr ) &&
+                end_of_stringp( c_cdr( car)) ) {
       // \todo check that car is of length 1
         result =
             make_string( pointer2cell( car ).payload.string.character, cdr );
@@ -1084,7 +1106,7 @@ throw_exception( struct cons_pointer message,
  * normally return. A function which detects a problem it cannot resolve
  * *should* return an exception.
  *
- * * (exception <message> <frame>)
+ * * (exception message frame)
  *
  * @param frame my stack frame.
  * @param frame_pointer a pointer to my stack_frame.

unit-tests/eval-quote-symbol.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-expected='(Special form)'
+expected='<Special form>'
 actual=`echo "(eval 'cond)" | target/psse | tail -1`
 
 if [ "${expected}" = "${actual}" ]

unit-tests/many-args.sh

@@ -6,7 +6,18 @@ actual=`echo "(+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)" | target/psse | tail -1`
 if [ "${expected}" = "${actual}" ]
 then
     echo "OK"
-    exit 0
+else
+    echo "Fail: expected '${expected}', got '${actual}'"
+    exit 1
+fi
+
+# check that all the args are actually being evaluated...
+expected="120"
+actual=`echo "(+ (+ 0 1) (+ 0 2) (+ 0 3) (+ 0 4) (+ 0 5) (+ 0 6) (+ 0 7) (+ 0 8) (+ 0 9) (+ 0 10) (+ 0 11) (+ 0 12) (+ 0 13) (+ 0 14 ) (+ 0 15))" | target/psse | tail -1`
+
+if [ "${expected}" = "${actual}" ]
+then
+    echo "OK"
 else
     echo "Fail: expected '${expected}', got '${actual}'"
     exit 1