From db58f43065c3b397754bb9efcb4a7376b2538131 Mon Sep 17 00:00:00 2001
From: LLLL Colonq <llll@colonq>
Date: Fri, 23 Oct 2026 20:47:43 -0400
Subject: pit: Add tests, fix binding bug

---
 pit/examples/6502.pit      | 174 +++++++++++++++++
 pit/examples/array.pit     |   2 +
 pit/examples/backtrace.pit |   2 +
 pit/examples/bif.pit       |  12 ++
 pit/examples/broken.pit    |   5 +
 pit/examples/compile.pit   |   6 +
 pit/examples/error.pit     |   1 +
 pit/examples/error2.pit    |   4 +
 pit/examples/fold.pit      |  12 ++
 pit/examples/gc.pit        |  13 ++
 pit/examples/infinite.pit  |   4 +
 pit/examples/int.pit       |   1 +
 pit/examples/loadpath.pit  |   2 +
 pit/examples/nonbroken.pit |   2 +
 pit/examples/recurse.pit   |   5 +
 pit/examples/struct.pit    |  11 ++
 pit/examples/test.pit      |  22 +++
 pit/examples/test10.pit    |   5 +
 pit/examples/test11.pit    |   4 +
 pit/examples/test2.pit     |   1 +
 pit/examples/test3.pit     |   7 +
 pit/examples/test4.pit     |   6 +
 pit/examples/test5.pit     |   6 +
 pit/examples/test6.pit     |   6 +
 pit/examples/test7.pit     |   1 +
 pit/examples/test8.pit     |   2 +
 pit/examples/test9.pit     |   2 +
 pit/examples/thebug.pit    |   9 +
 pit/examples/thebug2.pit   |  13 ++
 pit/examples/x86.pit       | 451 +++++++++++++++++++++++++++++++++++++++++++++
 pit/examples/y.pit         |   5 +
 31 files changed, 796 insertions(+)
 create mode 100644 pit/examples/6502.pit
 create mode 100644 pit/examples/array.pit
 create mode 100644 pit/examples/backtrace.pit
 create mode 100644 pit/examples/bif.pit
 create mode 100644 pit/examples/broken.pit
 create mode 100644 pit/examples/compile.pit
 create mode 100644 pit/examples/error.pit
 create mode 100644 pit/examples/error2.pit
 create mode 100644 pit/examples/fold.pit
 create mode 100644 pit/examples/gc.pit
 create mode 100644 pit/examples/infinite.pit
 create mode 100644 pit/examples/int.pit
 create mode 100644 pit/examples/loadpath.pit
 create mode 100644 pit/examples/nonbroken.pit
 create mode 100644 pit/examples/recurse.pit
 create mode 100644 pit/examples/struct.pit
 create mode 100644 pit/examples/test.pit
 create mode 100644 pit/examples/test10.pit
 create mode 100644 pit/examples/test11.pit
 create mode 100644 pit/examples/test2.pit
 create mode 100644 pit/examples/test3.pit
 create mode 100644 pit/examples/test4.pit
 create mode 100644 pit/examples/test5.pit
 create mode 100644 pit/examples/test6.pit
 create mode 100644 pit/examples/test7.pit
 create mode 100644 pit/examples/test8.pit
 create mode 100644 pit/examples/test9.pit
 create mode 100644 pit/examples/thebug.pit
 create mode 100644 pit/examples/thebug2.pit
 create mode 100644 pit/examples/x86.pit
 create mode 100644 pit/examples/y.pit

(limited to 'pit/examples')

diff --git a/pit/examples/6502.pit b/pit/examples/6502.pit
new file mode 100644
index 0000000..eb5a4e8
--- /dev/null
+++ b/pit/examples/6502.pit
@@ -0,0 +1,174 @@
+;;      (implicit )
+;;      (accumulator )
+;;      (immediate )
+;;      (zeropage )
+;;      (zeropage-x )
+;;      (zeropage-y )
+;;      (relative )
+;;      (absolute )
+;;      (absolute-x )
+;;      (absolute-y )
+;;      (indirect )
+;;      (indexed-indirect )
+;;      (indirect-indexed )
+
+(defun! 6502/ensure-u8 (x)
+  (if (and (>= x 0) (<= x 0xff))
+    (list x)
+    (error! "operand out of range")))
+
+(defun! 6502/ensure-i8 (x)
+  (cond 
+    ((and (>= x 0) (<= x 127)) (list x))
+    ((and (>= x -128) (< x 0)) (list (+ 0xff x)))
+    (error! "operand out of range")))
+
+(defun! 6502/ensure-u16 (x)
+  (if (and (>= (car x) 0) (<= (car x) 0xffff))
+    (list (bitwise/and 0xff x) (bitwise/and 0xff (bitwise/rshift x 8)))
+    (error! "operand out of range")))
+
+(defun! 6502/identify-operand (x)
+  (cond
+    ((equal? x nil) (cons 'implicit nil)) ;; (<op> )
+    ((equal? x '(a)) (cons 'accumulator nil)) ;; (<op> a)
+    ((integer? (car x)) (cons 'immediate (6502/ensure-u8 (car x)))) ;; (<op> 0x0f)
+    ((equal? (caar x) 'zeropage) ;; (<op> (zeropage 0x0f x))
+      (let ((zp (car x)))
+        (let ((a (6502/ensure-u8 (cadr zp))))
+          (case (caddr zp)
+            (x (cons 'zeropage-x a))
+            (y (cons 'zeropage-y a))
+            (nil (cons 'zeropage a))
+            (t (error! "unknown zeropage offset register"))))))
+    ((equal? (caar x) 'relative) ;; (<op> (relative 0x0f))
+      (cons 'relative (6502/ensure-i8 (cadar x))))
+    ((equal? (caar x) 'absolute) ;; (<op> (absolute 0x0f x))
+      (let ((ab (car x)))
+        (let ((a (6502/ensure-u16 (cadr ab))))
+          (case (caddr ab)
+            (x (cons 'absolute-x a))
+            (y (cons 'absolute-y a))
+            (nil (cons 'absolute a))
+            (t (error! "unknown absolute offset register"))))))
+    ((equal? (caar x) 'indirect)
+      (cons 'indirect (6502/ensure-u16 (cadar x))))
+    ((and (equal? (caar x) 'indexed-indirect) (equal? (caddar x) 'x))
+      (cons 'indexed-indirect (6502/ensure-u16 (cadar x))))
+    ((and (equal? (caar x) 'indirect-indexed) (equal? (caddar x) 'y))
+      (cons 'indexed-indirect (6502/ensure-u16 (cadar y))))
+    (t (error! "unknown operand"))))
+
+(defun! 6502/single (op)
+  (case op
+    ;; conditional branches
+    (bpl 0x10)
+    (bmi 0x30)
+    (bvc 0x50)
+    (bvs 0x70)
+    (bcc 0x90)
+    (bcs 0xb0)
+    (bne 0xd0)
+    (beq 0xf0)
+    ;; other instructions
+    (brk 0x00)
+    (jsr 0x20)
+    (rti 0x40)
+    (rts 0x60)
+    ;; other single-byte instructions
+    (php 0x08)
+    (clc 0x18)
+    (plp 0x28)
+    (sec 0x38)
+    (pha 0x48)
+    (cli 0x58)
+    (pla 0x68)
+    (sei 0x78)
+    (dey 0x88)
+    (tya 0x98)
+    (tay 0xa8)
+    (clv 0xb8)
+    (iny 0xc8)
+    (cld 0xd8)
+    (inx 0xe8)
+    (sed 0xf8)
+    (txa 0x8a)
+    (txs 0x9a)
+    (tax 0xaa)
+    (tsx 0xba)
+    (dex 0xca)
+    (nop 0xea)
+    (t (error! "invalid single-byte instruction"))))
+
+(defun! 6502/grouped (group opbits amodebits)
+  (bitwise/or
+    (bitwise/lshift (bitwise/and 0b111 opbits) 5)
+    (bitwise/lshift (bitwise/and 0b111 amodebits) 2)
+    group))
+
+(defun! 6502/group1 (op amode)
+  (6502/grouped 0b01
+    (case op
+      (ora 0b000)
+      (and 0b001)
+      (eor 0b010)
+      (adc 0b011)
+      (sta 0b100)
+      (lda 0b101)
+      (cmp 0b110)
+      (sbc 0b111)
+      (t (error! "invalid group 1 opcode")))
+    (case amode
+      (indexed-indirect 0b000)
+      (zeropage 0b001)
+      (immediate 0b010)
+      (absolute 0b011)
+      (indirect-indexed 0b100)
+      (zeropage-x 0b101)
+      (absolute-y 0b110)
+      (absolute-x 0b111)
+      (t (error! "invalid addressing mode for group 1")))))
+
+(defun! 6502/group2 (op amode)
+  (6502/grouped 0b10
+    (case op
+      (asl 0b000)
+      (rol 0b001)
+      (lsr 0b010)
+      (ror 0b011)
+      (stx 0b100)
+      (ldx 0b101)
+      (dec 0b110)
+      (inc 0b111)
+      (t (error! "invalid group 2 opcode")))
+    (cond
+      ((and (or (equal? op 'stx) (equal? op 'ldx)) (equal? amode 'zeropage-y)) 0b101)
+      ((and (equal? op 'ldx) (equal? amode 'absolute-y)) 0b111)
+      (t
+        (case amode
+          (immediate 0b000)
+          (zeropage 0b001)
+          (accumulator 0b010)
+          (absolute 0b011)
+          (zeropage-x 0b101)
+          (absolute-x 0b111)
+          (t (error! "invalid addressing mode for group 2")))))))
+
+(defun! 6502/group3 (op amode)
+  (6502/grouped 0b00
+    (case op
+      (bit 0b001)
+      (jmp 0b010)
+      (jmp-abs 0b011)
+      (sty 0b100)
+      (ldy 0b101)
+      (cpy 0b110)
+      (cpx 0b111)
+      (t (error! "invalid group 3 opcode")))
+    (case amode
+      (immediate 0b000)
+      (zeropage 0b001)
+      (absolute 0b011)
+      (zeropage-x 0b101)
+      (absolute-x 0b111)
+      (t (error! "invalid addressing mode for group 3")))))
diff --git a/pit/examples/array.pit b/pit/examples/array.pit
new file mode 100644
index 0000000..976f70d
--- /dev/null
+++ b/pit/examples/array.pit
@@ -0,0 +1,2 @@
+(print! (array/repeat 'foo 1000))
+(array/repeat 'foo 10000)
diff --git a/pit/examples/backtrace.pit b/pit/examples/backtrace.pit
new file mode 100644
index 0000000..8a44951
--- /dev/null
+++ b/pit/examples/backtrace.pit
@@ -0,0 +1,2 @@
+(defun! foo (x) (* x 2))
+(foo "bar")
\ No newline at end of file
diff --git a/pit/examples/bif.pit b/pit/examples/bif.pit
new file mode 100644
index 0000000..81a1248
--- /dev/null
+++ b/pit/examples/bif.pit
@@ -0,0 +1,12 @@
+(print! nil)
+(print! nil)
+(print! t)
+(print! (eq? 1 1))
+(diagnostics!)
+(defun! bif (x)
+  (cons x x))
+(diagnostics!)
+(setq! foo (print! (bif (bif (bif 67)))))
+(print! (eq? (car foo) (cdr foo)))
+(diagnostics!)
+(print! foo)
diff --git a/pit/examples/broken.pit b/pit/examples/broken.pit
new file mode 100644
index 0000000..09f4afc
--- /dev/null
+++ b/pit/examples/broken.pit
@@ -0,0 +1,5 @@
+;; (let ((foo (+ 1 1)))
+;;   (print! foo))
+((lambda (foo)
+   (print! foo))
+  (+ 1 1))
diff --git a/pit/examples/compile.pit b/pit/examples/compile.pit
new file mode 100644
index 0000000..37d7f57
--- /dev/null
+++ b/pit/examples/compile.pit
@@ -0,0 +1,6 @@
+(defmacro! foo ()
+  (setq! bar (lambda (x) (foo) (+ x 1)))
+  '(print 'hi))
+
+(foo)
+(print (funcall bar 1))
\ No newline at end of file
diff --git a/pit/examples/error.pit b/pit/examples/error.pit
new file mode 100644
index 0000000..58b7d99
--- /dev/null
+++ b/pit/examples/error.pit
@@ -0,0 +1 @@
+(print! "hello")
diff --git a/pit/examples/error2.pit b/pit/examples/error2.pit
new file mode 100644
index 0000000..63ab173
--- /dev/null
+++ b/pit/examples/error2.pit
@@ -0,0 +1,4 @@
+(defun! foo ()
+  (error! "yuck"))
+
+(foo)
diff --git a/pit/examples/fold.pit b/pit/examples/fold.pit
new file mode 100644
index 0000000..89031d0
--- /dev/null
+++ b/pit/examples/fold.pit
@@ -0,0 +1,12 @@
+(defun! foo (x)
+  (+ x 1))
+(print! (foo 1))
+(print! (funcall 'foo 1))
+(print! (list/map 'foo '(1 2 3)))
+(print! (list/foldl '+ 0 '(1 2 3)))
+(print! (list/take 2 '(1 2 3)))
+(print! (list/take 0 '(1 2 3)))
+(print! (list/take 100 '(1 2 3)))
+(print! (list/drop 2 '(1 2 3)))
+(print! (list/drop 10 '(1 2 3)))
+(print! (list/filter 'integer? '(1 foo 2 bar baz 3 quux)))
diff --git a/pit/examples/gc.pit b/pit/examples/gc.pit
new file mode 100644
index 0000000..28eed50
--- /dev/null
+++ b/pit/examples/gc.pit
@@ -0,0 +1,13 @@
+(diagnostics!)
+(setq! foo (cons 1 2))
+(setq! bar (cons foo 3))
+(setq! baz (cons bar foo))
+(diagnostics!)
+(print! foo)
+(setcar! foo baz)
+(print! (cdr (car (car foo))))
+(diagnostics!)
+(setq! foo nil)
+(setq! bar nil)
+(setq! baz nil)
+(diagnostics!)
diff --git a/pit/examples/infinite.pit b/pit/examples/infinite.pit
new file mode 100644
index 0000000..f815821
--- /dev/null
+++ b/pit/examples/infinite.pit
@@ -0,0 +1,4 @@
+(progn
+  (defun! foo ()
+    (foo))
+  foo)
\ No newline at end of file
diff --git a/pit/examples/int.pit b/pit/examples/int.pit
new file mode 100644
index 0000000..65646af
--- /dev/null
+++ b/pit/examples/int.pit
@@ -0,0 +1 @@
+(print! 0x10)
diff --git a/pit/examples/loadpath.pit b/pit/examples/loadpath.pit
new file mode 100644
index 0000000..5f8bcf8
--- /dev/null
+++ b/pit/examples/loadpath.pit
@@ -0,0 +1,2 @@
+;; (setq! *load-path* (list "test/"))
+(load! "test.pit")
\ No newline at end of file
diff --git a/pit/examples/nonbroken.pit b/pit/examples/nonbroken.pit
new file mode 100644
index 0000000..350f64f
--- /dev/null
+++ b/pit/examples/nonbroken.pit
@@ -0,0 +1,2 @@
+(+ 1
+  (fwefwfwfwe 1 1))
diff --git a/pit/examples/recurse.pit b/pit/examples/recurse.pit
new file mode 100644
index 0000000..8e1f784
--- /dev/null
+++ b/pit/examples/recurse.pit
@@ -0,0 +1,5 @@
+(defun! foo ()
+  (print! 'hi)
+  (foo))
+
+(foo)
\ No newline at end of file
diff --git a/pit/examples/struct.pit b/pit/examples/struct.pit
new file mode 100644
index 0000000..9e35654
--- /dev/null
+++ b/pit/examples/struct.pit
@@ -0,0 +1,11 @@
+(defstruct! foo
+  x
+  y
+  z)
+
+(setq! x (foo/new :y 10 :x 5 :z 111))
+(print! x)
+(print! (foo/get-y x))
+(foo/set-y! x 42)
+(print! (foo/get-y x))
+(print! (foo/get-z x))
diff --git a/pit/examples/test.pit b/pit/examples/test.pit
new file mode 100644
index 0000000..ef13abb
--- /dev/null
+++ b/pit/examples/test.pit
@@ -0,0 +1,22 @@
+(print! (list/map (lambda (x) (+ x 1)) (list 1 2 3 4 5)))
+(print! (eval! '(cons 1 2)))
+(defun! say-hi ()
+  (princ! "hello computer"))
+(say-hi)
+(setq! counter 42)
+(let ((counter 0))
+  (print! counter)
+  (fset! 'count (lambda () (setq! counter (+ counter 1))))
+  (fset! 'query (lambda () counter)))
+(print! (count)) (print! (query))
+(print! (count)) (print! (query))
+(defun! bar (x & xs)
+  (print! x)
+  (print! xs))
+(bar 1 2 3 4 5)
+(defun! baz (& kwargs)
+  (print! kwargs)
+  (let ((foo (plist/get :foo kwargs))
+         (bar (plist/get :bar kwargs)))
+    bar))
+(print! (baz :foo 10 :bar 5 :baz 3))
diff --git a/pit/examples/test10.pit b/pit/examples/test10.pit
new file mode 100644
index 0000000..0eea605
--- /dev/null
+++ b/pit/examples/test10.pit
@@ -0,0 +1,5 @@
+(list/find
+  (lambda (y)
+    (and (eq? (list/len y) 3)
+      (list/all? (lambda (x) (equal? x 2)) y)))
+  '((1 2 3) (2 2 2 2) (2 3 4) (2 2 2)))
\ No newline at end of file
diff --git a/pit/examples/test11.pit b/pit/examples/test11.pit
new file mode 100644
index 0000000..83d4816
--- /dev/null
+++ b/pit/examples/test11.pit
@@ -0,0 +1,4 @@
+(print! 'here)
+(list/foldl '+ 0 '(1 2 3))
+(print! 'there)
+(print! (list/foldl '+ 0 '(1 2 3)))
\ No newline at end of file
diff --git a/pit/examples/test2.pit b/pit/examples/test2.pit
new file mode 100644
index 0000000..a86f8d2
--- /dev/null
+++ b/pit/examples/test2.pit
@@ -0,0 +1 @@
+(print! "hello from test2")
diff --git a/pit/examples/test3.pit b/pit/examples/test3.pit
new file mode 100644
index 0000000..1964242
--- /dev/null
+++ b/pit/examples/test3.pit
@@ -0,0 +1,7 @@
+(let ((bs (bs/new!)))
+  (print! bs)
+  ;; (bs/grow! 1 bs)
+  (bs/write8! bs 0 67)
+  (bs/spit! "test3.bin" bs)
+  ;; (bs/delete! bs)
+  )
diff --git a/pit/examples/test4.pit b/pit/examples/test4.pit
new file mode 100644
index 0000000..ef8e04c
--- /dev/null
+++ b/pit/examples/test4.pit
@@ -0,0 +1,6 @@
+(print!
+  (or
+    (case 'baz
+      (foo 1)
+      (bar 2))
+    3))
\ No newline at end of file
diff --git a/pit/examples/test5.pit b/pit/examples/test5.pit
new file mode 100644
index 0000000..2ad3675
--- /dev/null
+++ b/pit/examples/test5.pit
@@ -0,0 +1,6 @@
+(defun! foo (x)
+  (if (equal? 0 (% x 10000))
+    (print! x))
+  (foo (+ x 1)))
+
+(foo 0)
\ No newline at end of file
diff --git a/pit/examples/test6.pit b/pit/examples/test6.pit
new file mode 100644
index 0000000..cb04f22
--- /dev/null
+++ b/pit/examples/test6.pit
@@ -0,0 +1,6 @@
+(print!
+  ((case 'baz
+    (foo (lambda (x) (+ x 1)))
+    (bar (lambda (x) (+ x 2))))
+    3))
+  
\ No newline at end of file
diff --git a/pit/examples/test7.pit b/pit/examples/test7.pit
new file mode 100644
index 0000000..48d2c2c
--- /dev/null
+++ b/pit/examples/test7.pit
@@ -0,0 +1 @@
+(print! (list/map (lambda (x) (+ x 1)) '(1 2 3)))
\ No newline at end of file
diff --git a/pit/examples/test8.pit b/pit/examples/test8.pit
new file mode 100644
index 0000000..3b41d7a
--- /dev/null
+++ b/pit/examples/test8.pit
@@ -0,0 +1,2 @@
+(defun! foo (x) (+ x 1))
+(foo 2)
\ No newline at end of file
diff --git a/pit/examples/test9.pit b/pit/examples/test9.pit
new file mode 100644
index 0000000..daf1686
--- /dev/null
+++ b/pit/examples/test9.pit
@@ -0,0 +1,2 @@
+(defun! foo (x) x)
+(foo 1)
\ No newline at end of file
diff --git a/pit/examples/thebug.pit b/pit/examples/thebug.pit
new file mode 100644
index 0000000..ad87bd7
--- /dev/null
+++ b/pit/examples/thebug.pit
@@ -0,0 +1,9 @@
+(defun! foo (x)
+  (lambda (y)
+    (+ x y)))
+
+(setq! bar (foo 10))
+(setq! baz (foo 100))
+
+(print! (funcall bar 4))
+
diff --git a/pit/examples/thebug2.pit b/pit/examples/thebug2.pit
new file mode 100644
index 0000000..2376ff8
--- /dev/null
+++ b/pit/examples/thebug2.pit
@@ -0,0 +1,13 @@
+
+(setq! z 40)
+(setq! f
+  (lambda (x)
+    (lambda (y)
+      (lambda (w)
+        (+
+          (funcall (lambda (z) (+ x y z)) 3)
+          w
+          z)))))
+(let ((z 20))
+  (print! (funcall (funcall (funcall f 1) 2) 3)))
+
diff --git a/pit/examples/x86.pit b/pit/examples/x86.pit
new file mode 100644
index 0000000..2aa8d89
--- /dev/null
+++ b/pit/examples/x86.pit
@@ -0,0 +1,451 @@
+(defun! x86/split16le (w)
+  "Split the 16-bit W16 into a little-endian list of 8-bit integers."
+  (list
+    (bitwise/and 0xff w)
+    (bitwise/and 0xff (bitwise/rshift w 8))))
+
+(defun! x86/split32le (w)
+  "Split the 32-bit W32 into a little-endian list of 8-bit integers."
+  (list
+   (bitwise/and 0xff w)
+   (bitwise/and 0xff (bitwise/rshift w 8))
+   (bitwise/and 0xff (bitwise/rshift w 16))
+   (bitwise/and 0xff (bitwise/rshift w 24))))
+
+(defun! x86/register-1byte? (r)
+  "Return the register index for 1-byte register R."
+  (case r
+    (al 0) (cl 1) (dl 2) (bl 3)
+    (ah 4) (ch 5) (dh 6) (bh 7)
+    (r8b 8) (r9b 9) (r10b 10) (r11b 11)
+    (r12b 12) (r13b 13) (r14b 14) (r15b 15)))
+
+(defun! x86/register-2byte? (r)
+  "Return the register index for 2-byte register R."
+  (case r
+    (ax 0) (cx 1) (dx 2) (bx 3)
+    (sp 4) (bp 5) (si 6) (di 7)
+    (r8w 8) (r9w 9) (r10w 10) (r11w 11)
+    (r12w 12) (r13w 13) (r14w 14) (r15w 15)))
+
+(defun! x86/register-4byte? (r)
+  "Return the register index for 4-byte register R."
+  (case r
+    (eax 0) (ecx 1) (edx 2) (ebx 3)
+    (esp 4) (ebp 5) (esi 6) (edi 7)
+    (r8d 8) (r9d 9) (r10d 10) (r11d 11)
+    (r12d 12) (r13d 13) (r14d 14) (r15d 15)))
+
+(defun! x86/register-8byte? (r)
+  "Return the register index for 8-byte register R."
+  (case r
+    (rax 0) (rcx 1) (rdx 2) (rbx 3)
+    (rsp 4) (rbp 5) (rsi 6) (rdi 7)
+    (r8 8) (r9 9) (r10 10) (r11 11)
+    (r12 12) (r13 13) (r14 14) (r15 15)))
+
+(defun! x86/register? (r)
+  "Return the register index of R."
+  (or
+    (x86/register-1byte? r)
+    (x86/register-2byte? r)
+    (x86/register-4byte? r)
+    (x86/register-8byte? r)))
+
+(defun! x86/register-extended? (r)
+  "Return non-nil if R is an extended register."
+  (list/contains? r
+    '( r8b r9b r10b r11b r12b r13b r14b r15b
+       r8w r9w r10w r11w r12w r13w r14w r15w
+       r8d r9d r10d r11d r12d r13d r14d r15d
+       r8 r9 r10 r11 r12 r13 r14 r15)))
+
+(defun! x86/integer-fits-in-bits? (bits x)
+  "Determine if X fits in BITS."
+  (if (integer? x)
+    (let ((leftover (bitwise/rshift x bits)))
+      (eq? leftover 0))))
+(defun! x86/operand-immediate-fits? (sz x)
+  "Determine if immediate operand X fits in SZ."
+  (let
+    ((bits
+       (or
+         (case sz
+           ("b" 8) ("c" 16) ("d" 32) ("i" 16)
+           ("j" 32) ("q" 64) ("v" 64) ("w" 16)
+           ("y" 64) ("z" 32))
+         (error! "unknown operand pattern size"))))
+    (x86/integer-fits-in-bits? bits x)))
+
+(defun! x86/operand-register-fits? (sz r)
+  "Determine if register operand R fits in SZ."
+  (case sz
+    ("b" (x86/register-1byte? r))
+    ("c" (or (x86/register-1byte? r) (x86/register-2byte? r)))
+    ("d" (x86/register-4byte? r))
+    ("i" (x86/register-2byte? r))
+    ("j" (x86/register-4byte? r))
+    ("q" (x86/register-8byte? r))
+    ("v" (or (x86/register-2byte? r) (x86/register-4byte? r) (x86/register-8byte? r)))
+    ("w" (x86/register-2byte? r))
+    ("y" (or (x86/register-4byte? r) (x86/register-8byte? r)))
+    ("z" (or (x86/register-2byte? r) (x86/register-4byte? r)))))
+
+(defun! x86/memory-operand-base (m)
+  (and
+    (eq? (car m) 'mem)
+    (car (cdr m))))
+(defun! x86/memory-operand-off (m)
+  (and
+    (eq? (car m) 'mem)
+    (or (car (cdr (cdr m))) 0)))
+
+(defun! x86/operand-memory-location? (op)
+  "Return non-nil if OP represents a memory location."
+  (let ( (base (x86/memory-operand-base op))
+         (off (x86/memory-operand-off op)))
+    (and
+      (or (x86/register-4byte? base) (x86/register-8byte? base))
+      (integer? off))))
+
+(defun! x86/operand-match? (pat op)
+  "Determine if operand OP matches PAT."
+  (cond
+    ((symbol? pat) (eq? pat op))
+    ((cons? pat) (list/contains? op pat))
+    ((bytes? pat)
+      (let ( (loc (bytes/range 0 1 pat))
+             (sz (bytes/range 1 (bytes/len pat) pat)))
+        (cond
+          ((or (equal? loc "I") (equal? loc "J")) (x86/operand-immediate-fits? sz op))
+          ((or (equal? loc "G") (equal? loc "R")) (x86/operand-register-fits? sz op))
+          ((equal? loc "M") (x86/operand-memory-location? op))
+          ((equal? loc "E")
+            (or (x86/operand-register-fits? sz op) (x86/operand-memory-location? op)))
+          (t (error! "unknown operand pattern location")))))))
+
+(defun! x86/operand-size (op)
+  "Return the minimum power-of-2 size in bytes that contains OP."
+  (cond
+    ((symbol? op)
+      (cond
+        ((x86/register-1byte? op) 1)
+        ((x86/register-2byte? op) 2)
+        ((x86/register-4byte? op) 4)
+        ((x86/register-8byte? op) 8)
+        (t (error! "attempted to take size of unknown register"))))
+    ((integer? op)
+      (cond
+        ((x86/integer-fits-in-bits? 8 op) 1)
+        ((x86/integer-fits-in-bits? 16 op) 2)
+        ((x86/integer-fits-in-bits? 32 op) 4)
+        ((x86/integer-fits-in-bits? 64 op) 8)
+        (t (error! "attempted to take size of too-large immediate"))))
+    ((x86/operand-memory-location? op) 1)
+    (t (error! "attempted to take size of unknown operand"))))
+
+(defstruct! x86/ins
+  operand-size-prefix
+  address-size-prefix
+  rex-w
+  rex-r
+  rex-x
+  rex-b
+  opcode
+  modrm-mod
+  modrm-reg
+  modrm-rm
+  disp ;; pair of size and value
+  imm ;; pair of size and value
+  )
+
+(defun! x86/ins-bytes (ins)
+  "Return a list of bytes encoding INS."
+  (let ( (opcode (x86/ins/get-opcode ins))
+         (rex-w (x86/ins/get-rex-w ins))
+         (rex-r (x86/ins/get-rex-r ins))
+         (rex-x (x86/ins/get-rex-x ins))
+         (rex-b (x86/ins/get-rex-b ins))
+         (modrm-mod (x86/ins/get-modrm-mod ins))
+         (modrm-reg (x86/ins/get-modrm-reg ins))
+         (modrm-rm (x86/ins/get-modrm-rm ins))
+         (disp (x86/ins/get-disp ins))
+         (imm (x86/ins/get-imm ins)))
+    (list/append
+      (if (x86/ins/get-operand-size-prefix ins) '(0x66))
+      (if (x86/ins/get-address-size-prefix ins) '(0x67))
+      (if (or rex-w rex-r rex-x rex-b)
+        (list
+          (bitwise/or
+            0x40
+            (if rex-w 0b1000 0)
+            (if rex-r 0b0100 0)
+            (if rex-x 0b0010 0)
+            (if rex-b 0b0001 0))))
+      (cond
+        ((not opcode) (error! "no opcode for instruction"))
+        ((cons? opcode) opcode)
+        ((integer? opcode) (list opcode))
+        (t (error! "malformed opcode for instruction")))
+      (if (or modrm-mod modrm-reg modrm-rm)
+        (list
+          (bitwise/or
+            (bitwise/lshift (or modrm-mod 0) 6)
+            (bitwise/lshift (or modrm-reg 0) 3)
+            (or modrm-rm 0))))
+      (if disp
+        (cond
+          ((eq? (car disp) 1) (list (cdr disp)))
+          ((eq? (car disp) 4) (x86/split32le (cdr disp)))
+          (t (error! "malformed displacement for instruction"))))
+      (if imm
+        (cond
+          ((eq? (car imm) 1) (list (cdr imm)))
+          ((eq? (car imm) 2) (x86/split16le (cdr imm)))
+          ((eq? (car imm) 4) (x86/split32le (cdr imm)))
+          (t (error! "malformed immediate for instruction")))))))
+
+(defun! x86/instruction-update-sizes (ins ops default-size)
+  "Update INS to account for the sizes of OPS.
+DEFAULT-SIZE is the default operand size."
+  (let ((defsz (or default-size 4)))
+    (if (> (list/len ops) 0)
+      (let ((regs (list/uniq (list/map 'x86/operand-size (list/filter 'x86/register? ops)))))
+        (if (> (list/len regs) 1)
+          (error! "invalid mix of register sizes in operands"))
+        (let ((sz (if (eq? (list/len regs) 0) defsz (car regs))))
+          (cond
+            ((eq? sz 1) nil)
+            ((eq? defsz sz) nil)
+            ((and (not (eq? defsz 2)) (eq? sz 2)) (x86/ins/set-operand-size-prefix! ins t))
+            ((and (not (eq? defsz 8)) (eq? sz 8)) (x86/ins/set-rex-w! ins t))
+            (t (error! "unable to encode operands with default size")))
+          sz)))))
+
+(defun! x86/instruction-update-operand (esz ins pat op)
+  "Update INS to account for an operand OP according to PAT.
+The effective operand size is ESZ."
+  (cond
+    ((bytes? pat)
+      (let ((loc (bytes/range 0 1 pat)))
+        (cond
+          ((equal? loc "I")
+            (let ((immsz (if (>= esz 4) 4 esz)))
+              (if (not (x86/integer-fits-in-bits? (* 8 immsz) op))
+                (error! "Immediate too large" op))
+              (x86/ins/set-imm! ins (cons immsz op))))
+          ((equal? loc "J")
+            (let ((immsz (if (eq? esz 1) 1 4)))
+              (if (not (x86/integer-fits-in-bits? (* 8 immsz) op))
+                (error! "jump displacement too large"))
+              (x86/ins/set-disp! ins (cons immsz op))))
+          ((equal? loc "G")
+            (x86/ins/set-modrm-reg! ins
+              (or (x86/register? op) (error "Invalid register: %s" op))))
+          ((or (equal? loc "R") (and (equal? loc "E") (x86/register? op)))
+            (x86/ins/set-modrm-mod! ins 0b11)
+            (x86/ins/set-modrm-rm! ins
+              (or (x86/register? op) (error "Invalid register: %s" op))))
+          ((or (equal? loc "M") (and (equal? loc "E") (x86/operand-memory-location? op)))
+            (let ( (base (x86/memory-operand-base op))
+                   (off (x86/memory-operand-off op)))
+              (cond
+                ((eq? base 'eip)
+                  (x86/ins/set-modrm-rm! ins 0b101)
+                  (x86/ins/set-modrm-mod! ins 0b00)
+                  (x86/ins/set-disp! ins (cons 4 off))
+                  (x86/ins/set-address-size-prefix! ins t))
+                ((eq? base 'rip)
+                  (x86/ins/set-modrm-rm! ins 0b101)
+                  (x86/ins/set-modrm-mod! ins 0b00)
+                  (x86/ins/set-disp! ins (cons 4 off)))
+                (t
+                  (x86/ins/set-modrm-rm! ins
+                    (or
+                      (x86/register-4byte? base)
+                      (x86/register-8byte? base)
+                      (error! "invalid base register")))
+                  (if (x86/register-4byte? base)
+                    (x86/ins/set-address-size-prefix! ins t))
+                  (cond
+                    ((x86/integer-fits-in-bits? 8 off)
+                      (x86/ins/set-disp! ins (cons 1 off))
+                      (x86/ins/set-modrm-mod! ins 0b01))
+                    ((x86/integer-fits-in-bits? 32 off)
+                      (x86/ins/set-disp! ins (cons 4 off))
+                      (x86/ins/set-modrm-mod! ins 0b10))
+                    (t (error! "invalid offset")))))))
+          (t (error! "invalid operand location code")))))))
+
+(defun! x86/default-instruction-handler (opcode & kwargs)
+  "Return an instruction handler for OPCODE.
+The instruction handler will run POSTHOOK on the instruction at the end.
+DEFAULT-SIZE is the default operand size."
+  (let ( (posthook (plist/get :posthook kwargs))
+         (default-size (plist/get :default-size kwargs)))
+    (lambda (pats ops)
+      (let ((ret (x86/ins/new :opcode opcode)))
+        (let ((esz
+                (or (x86/instruction-update-sizes ret ops default-size)
+                  (error! "malformed size for operands"))))
+          (list/zip-with
+            (lambda (it other)
+              (x86/instruction-update-operand esz ret it other))
+            pats
+            ops))
+        (if posthook
+          (funcall posthook ret ops))
+        ret))))
+
+(defun! x86/instruction-handler-jcc (opcode immsz)
+  "Return an instruction handler for a Jcc instruction at OPCODE.
+IMMSZ is the size of the displacement from RIP."
+  (lambda (_pats ops)
+    (let ((ret (x86/ins/new :opcode opcode)))
+      (x86/ins/set-disp! ret (cons immsz (car ops)))
+      ret)))
+
+(defun! x86/generate-handlers-arith (opbase group1reg)
+  "Return handlers for an arithmetic mnemonic starting at OPBASE.
+The REG value in ModR/M is indicated by GROUP1REG."
+  (list
+    (cons '("Eb" "Gb") (x86/default-instruction-handler (+ opbase 0)))
+    (cons '("Ev" "Gv") (x86/default-instruction-handler (+ opbase 1)))
+    (cons '("Gb" "Eb") (x86/default-instruction-handler (+ opbase 2)))
+    (cons '("Gv" "Ev") (x86/default-instruction-handler (+ opbase 3)))
+    (cons '(al "Ib") (x86/default-instruction-handler (+ opbase 4)))
+    (cons '((ax eax rax) "Iz") (x86/default-instruction-handler (+ opbase 5)))
+    (cons '("Eb" "Ib")
+      (x86/default-instruction-handler 0x80
+        :posthook (lambda (ins _) (x86/ins/set-modrm-reg! ins group1reg))))
+    (cons '("Ev" "Iz")
+      (x86/default-instruction-handler 0x81
+        :posthook (lambda (ins _) (x86/ins/set-modrm-reg! ins group1reg))))
+    (cons '("Ev" "Ib")
+      (x86/default-instruction-handler 0x83
+        :posthook (lambda (ins _) (setf (x86/ins-modrm-reg ins) group1reg))))))
+
+(setq! x86/registers-+reg-base
+  '( (+rb . (al cl dl bl ah ch dh bh))
+     (+rw . (ax cx dx bx sp bp si di))
+     (+rd . (eax ecx edx ebx esp ebp esi edi))
+     (+rq . (rax rcx rdx rbx rsp rbp rsi rdi))))
+(setq! x86/registers-+reg-extended
+  '( (+rw . (r8b r9b r10b r11b r12b r13b r14b r15b))
+     (+rw . (r8w r9w r10w r11w r12w r13w r14w r15w))
+     (+rd . (r8d r9d r10d r11d r12d r13d r14d r15d))
+     (+rq . (r8 r9 r10 r11 r12 r13 r14 r15))))
+(defun! x86/generate-handlers-opcode-+reg (opbase extraops addends & args)
+  "Generate handlers for a family of opcodes that uses the +reg encoding.
+OPBASE is the base opcode.
+EXTRAOPS are additional operands after the register operand.
+ADDENDS is a list of symbols like +rw, +rq etc. that denote allowed registers.
+ARGS are passed verbatim to `u/x86/default-instruction-handler."
+  (list/map
+    (lambda (it)
+      (let ( (abase (list/map (lambda (a) (list/nth it (alist/get a x86/registers-+reg-base))) addends))
+             (aext (list/map (lambda (a) (list/nth it (alist/get a x86/registers-+reg-extended))) addends)))
+        (cons
+          (cons (list/append abase aext) extraops)
+          (apply 'x86/default-instruction-handler (cons (+ opbase it) args)))))
+    (list/iota 8)))
+
+(setq!
+  x86/mnemonic-table
+  (list
+    (cons 'add (x86/generate-handlers-arith 0x00 0))
+    (cons 'or  (x86/generate-handlers-arith 0x08 1))
+    (cons 'adc (x86/generate-handlers-arith 0x10 2))
+    (cons 'sbb (x86/generate-handlers-arith 0x18 3))
+    (cons 'and (x86/generate-handlers-arith 0x20 4))
+    (cons 'sub (x86/generate-handlers-arith 0x28 5))
+    (cons 'xor (x86/generate-handlers-arith 0x30 6))
+    (cons 'cmp (x86/generate-handlers-arith 0x38 7))
+    (cons 'push
+      (x86/generate-handlers-opcode-+reg 0x50 '() '(+rw +rq) 
+        :default-size 8
+        :posthook (lambda (ins ops) (x86/ins/set-rex-b! ins (x86/register-extended? (car ops))))))
+    (cons 'pop
+      (x86/generate-handlers-opcode-+reg 0x58 '() '(+rw +rq)
+        :default-size 8
+        :posthook (lambda (ins ops) (x86/ins/set-rex-b! ins (x86/register-extended? (car ops))))))
+    (list 'jo
+      (cons '("Jb") (x86/instruction-handler-jcc 0x70 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x80) 4)))
+    (list 'jno
+      (cons '("Jb") (x86/instruction-handler-jcc 0x71 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x81) 4)))
+    (list 'jb
+      (cons '("Jb") (x86/instruction-handler-jcc 0x72 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x82) 4)))
+    (list 'jnb
+      (cons '("Jb") (x86/instruction-handler-jcc 0x73 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x83) 4)))
+    (list 'jz
+      (cons '("Jb") (x86/instruction-handler-jcc 0x74 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x84) 4)))
+    (list 'jnz
+      (cons '("Jb") (x86/instruction-handler-jcc 0x75 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x85) 4)))
+    (list 'jbe
+      (cons '("Jb") (x86/instruction-handler-jcc 0x76 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x86) 4)))
+    (list 'jnbe
+      (cons '("Jb") (x86/instruction-handler-jcc 0x77 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x87) 4)))
+    (list 'js
+      (cons '("Jb") (x86/instruction-handler-jcc 0x78 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x88) 4)))
+    (list 'jns
+      (cons '("Jb") (x86/instruction-handler-jcc 0x79 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x89) 4)))
+    (list 'jp
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7a 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8a) 4)))
+    (list 'jnp
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7b 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8b) 4)))
+    (list 'jl
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7c 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8c) 4)))
+    (list 'jnl
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7d 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8d) 4)))
+    (list 'jle
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7e 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8e) 4)))
+    (list 'jnle
+      (cons '("Jb") (x86/instruction-handler-jcc 0x7f 1))
+      (cons '("Jz") (x86/instruction-handler-jcc '(0x0f 0x8f) 4)))
+    (cons 'mov
+      (x86/generate-handlers-opcode-+reg 0xb0 '("Ib") '(+rb)
+        :posthook (lambda (ins ops) (x86/ins/set-rex-b! ins (x86/register-extended? (car ops))))))
+    (cons 'mov
+      (x86/generate-handlers-opcode-+reg 0xb8 '("Iv") '(+rw +rd +rq)
+        :posthook (lambda (ins ops) (x86/ins/set-rex-b! ins (x86/register-extended? (car ops))))))
+    (list 'jmp
+      (cons '("Ev")
+        (x86/default-instruction-handler 0xff
+          :default-size 8
+          :posthook (lambda (ins _) (setf (u/x86/ins-modrm-reg ins) 4)))))
+    (list 'syscall
+      (cons '() (lambda (_ _) (x86/ins/new :opcode '(0x0f 0x05)))))
+    ))
+
+(defun! x86/asm (op)
+  "Assemble OP to an instruction."
+  (let ((mnem (car op)) (operands (cdr op)))
+    (let ((variants (or (alist/get mnem x86/mnemonic-table) (error! "unknown mnemonic"))))
+      (let ((v
+              (list/find
+                (lambda (it)
+                  (and (eq? (list/len (car it)) (list/len operands))
+                    (list/all? (lambda (x) x) (list/zip-with 'x86/operand-match? (car it) operands))))
+                variants)))
+        (if (and v (function? (cdr v)))
+          (funcall (cdr v) (car v) operands)
+          (error! "could not identify instruction"))))))
+
+(setq! test-ins (x86/asm '(syscall)))
+(print! test-ins)
+(print! (x86/ins-bytes test-ins))
diff --git a/pit/examples/y.pit b/pit/examples/y.pit
new file mode 100644
index 0000000..5e9218b
--- /dev/null
+++ b/pit/examples/y.pit
@@ -0,0 +1,5 @@
+(setq! Y
+  (lambda (f)
+    (funcall
+      (lambda (x) (funcall f (funcall x x)))
+      (lambda (x) (funcall f (funcall x x))))))
-- 
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