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1 files changed, 151 insertions, 0 deletions

diff --git a/apps/rpn.mu b/apps/rpn.mu
new file mode 100644
index 00000000..1f432365
--- /dev/null
+++ b/apps/rpn.mu
@@ -0,0 +1,151 @@
+# Integer arithmetic using postfix notation
+#
+# Limitations:
+#   Division not implemented yet.
+#
+# To build:
+#   $ ./translate apps/rpn.mu
+#
+# Example session:
+#   $ qemu-system-i386 code.img
+#   > 4
+#   4
+#   > 5 3 -
+#   2
+#
+# Error handling is non-existent. This is just a prototype.
+
+fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk) {
+  var in-storage: (stream byte 0x80)
+  var in/esi: (addr stream byte) <- address in-storage
+  var y/ecx: int <- copy 0
+  var space/edx: grapheme <- copy 0x20
+  # read-eval-print loop
+  {
+    # print prompt
+    var x/eax: int <- draw-text-rightward screen, "> ", 0/x, 0x80/xmax, y, 3/fg/cyan, 0/bg
+    # read line from keyboard
+    clear-stream in
+    {
+      draw-cursor screen, space
+      var key/eax: byte <- read-key keyboard
+      compare key, 0xa/newline
+      break-if-=
+      compare key, 0
+      loop-if-=
+      var key2/eax: int <- copy key
+      append-byte in, key2
+      var g/eax: grapheme <- copy key2
+      draw-grapheme-at-cursor screen, g, 0xf/fg, 0/bg
+      move-cursor-right 0
+      loop
+    }
+    # clear cursor
+    draw-grapheme-at-cursor screen, space, 3/fg/never-used, 0/bg
+    # parse and eval
+    var out/eax: int <- simplify in
+    # print
+    y <- increment
+    out, y <- draw-int32-decimal-wrapping-right-then-down screen, out, 0/xmin, y, 0x80/xmax, 0x30/ymax, 0/x, y, 7/fg, 0/bg
+    # newline
+    y <- increment
+    #
+    loop
+  }
+}
+
+type int-stack {
+  data: (handle array int)
+  top: int
+}
+
+fn simplify in: (addr stream byte) -> _/eax: int {
+  var word-storage: slice
+  var word/ecx: (addr slice) <- address word-storage
+  var stack-storage: int-stack
+  var stack/esi: (addr int-stack) <- address stack-storage
+  initialize-int-stack stack, 0x10
+  $simplify:word-loop: {
+    next-word in, word
+    var done?/eax: boolean <- slice-empty? word
+    compare done?, 0
+    break-if-!=
+    # if word is an operator, perform it
+    {
+      var is-add?/eax: boolean <- slice-equal? word, "+"
+      compare is-add?, 0
+      break-if-=
+      var _b/eax: int <- pop-int-stack stack
+      var b/edx: int <- copy _b
+      var a/eax: int <- pop-int-stack stack
+      a <- add b
+      push-int-stack stack, a
+      loop $simplify:word-loop
+    }
+    {
+      var is-sub?/eax: boolean <- slice-equal? word, "-"
+      compare is-sub?, 0
+      break-if-=
+      var _b/eax: int <- pop-int-stack stack
+      var b/edx: int <- copy _b
+      var a/eax: int <- pop-int-stack stack
+      a <- subtract b
+      push-int-stack stack, a
+      loop $simplify:word-loop
+    }
+    {
+      var is-mul?/eax: boolean <- slice-equal? word, "*"
+      compare is-mul?, 0
+      break-if-=
+      var _b/eax: int <- pop-int-stack stack
+      var b/edx: int <- copy _b
+      var a/eax: int <- pop-int-stack stack
+      a <- multiply b
+      push-int-stack stack, a
+      loop $simplify:word-loop
+    }
+    # otherwise it's an int
+    var n/eax: int <- parse-decimal-int-from-slice word
+    push-int-stack stack, n
+    loop
+  }
+  var result/eax: int <- pop-int-stack stack
+  return result
+}
+
+fn initialize-int-stack _self: (addr int-stack), n: int {
+  var self/esi: (addr int-stack) <- copy _self
+  var d/edi: (addr handle array int) <- get self, data
+  populate d, n
+  var top/eax: (addr int) <- get self, top
+  copy-to *top, 0
+}
+
+fn push-int-stack _self: (addr int-stack), _val: int {
+  var self/esi: (addr int-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  var data-ah/edx: (addr handle array int) <- get self, data
+  var data/eax: (addr array int) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-addr/edx: (addr int) <- index data, top
+  var val/eax: int <- copy _val
+  copy-to *dest-addr, val
+  add-to *top-addr, 1
+}
+
+fn pop-int-stack _self: (addr int-stack) -> _/eax: int {
+  var self/esi: (addr int-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  {
+    compare *top-addr, 0
+    break-if->
+    return 0
+  }
+  subtract-from *top-addr, 1
+  var data-ah/edx: (addr handle array int) <- get self, data
+  var data/eax: (addr array int) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var result-addr/eax: (addr int) <- index data, top
+  var val/eax: int <- copy *result-addr
+  return val
+}