From 8bb22dcb0a3819c1cc22299aec8126a701a3267d Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Thu, 11 Feb 2021 21:11:41 -0800
Subject: 7725 - baremetal/shell: start on evaluator

---
 baremetal/shell/eval.mu        |  36 +++++++++++
 baremetal/shell/value-stack.mu | 138 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 174 insertions(+)
 create mode 100644 baremetal/shell/eval.mu
 create mode 100644 baremetal/shell/value-stack.mu

(limited to 'baremetal/shell')

diff --git a/baremetal/shell/eval.mu b/baremetal/shell/eval.mu
new file mode 100644
index 00000000..2506bd22
--- /dev/null
+++ b/baremetal/shell/eval.mu
@@ -0,0 +1,36 @@
+# evaluator for the Mu shell language
+# inputs:
+#   a list of lines, each a list of words, each an editable gap-buffer
+#   end: a word to stop at
+# output:
+#   a stack of values to render that summarizes the result of evaluation until 'end'
+
+# Key features of the language:
+#   { and } for grouping words
+#   break and loop for control flow within groups
+#   -> for conditionally skipping the next word or group
+
+# Example: Pushing numbers from 1 to n on the stack (single-line body with
+# conditionals and loops)
+#
+#   3 =n
+#   { n 1 <     -> break n n 1- =n loop }
+# stack:
+#     3 1 false          3 3 2  3   1
+#       3                  3 3      2
+#                                   3
+
+# Rules beyond simple postfix:
+#   If the final word is `->`, clear stack
+#   If the final word is `break`, pop top of stack
+#
+#   `{` and `}` don't affect evaluation
+#   If the final word is `{` or `}`, clear stack
+#
+#   If `->` in middle and top of stack is falsy, skip next word or group
+#
+#   If `break` in middle executes, skip to next containing `}`
+#     If no containing `}`, clear stack (incomplete)
+#
+#   If `loop` in middle executes, skip to previous containing `{`
+#     If no containing `}`, clear stack (error)
diff --git a/baremetal/shell/value-stack.mu b/baremetal/shell/value-stack.mu
new file mode 100644
index 00000000..c456f2e5
--- /dev/null
+++ b/baremetal/shell/value-stack.mu
@@ -0,0 +1,138 @@
+type value-stack {
+  data: (handle array value)
+  top: int
+}
+
+fn initialize-value-stack _self: (addr value-stack), n: int {
+  var self/esi: (addr value-stack) <- copy _self
+  var d/edi: (addr handle array value) <- get self, data
+  populate d, n
+  var top/eax: (addr int) <- get self, top
+  copy-to *top, 0
+}
+
+fn clear-value-stack _self: (addr value-stack) {
+  var self/esi: (addr value-stack) <- copy _self
+  var top/eax: (addr int) <- get self, top
+  copy-to *top, 0
+}
+
+fn push-number-to-value-stack _self: (addr value-stack), _val: float {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  var data-ah/edx: (addr handle array value) <- get self, data
+  var data/eax: (addr array value) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-offset/edx: (offset value) <- compute-offset data, top
+  var dest-addr/edx: (addr value) <- index data, dest-offset
+  var dest-addr2/eax: (addr float) <- get dest-addr, number-data
+  var val/xmm0: float <- copy _val
+  copy-to *dest-addr2, val
+  increment *top-addr
+  var type-addr/eax: (addr int) <- get dest-addr, type
+  copy-to *type-addr, 0/number
+}
+
+fn push-string-to-value-stack _self: (addr value-stack), val: (handle array byte) {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  var data-ah/edx: (addr handle array value) <- get self, data
+  var data/eax: (addr array value) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-offset/edx: (offset value) <- compute-offset data, top
+  var dest-addr/edx: (addr value) <- index data, dest-offset
+  var dest-addr2/eax: (addr handle array byte) <- get dest-addr, text-data
+  copy-handle val, dest-addr2
+  var dest-addr3/eax: (addr int) <- get dest-addr, type
+  copy-to *dest-addr3, 1/string
+  increment *top-addr
+}
+
+fn push-array-to-value-stack _self: (addr value-stack), val: (handle array value) {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  var data-ah/edx: (addr handle array value) <- get self, data
+  var data/eax: (addr array value) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-offset/edx: (offset value) <- compute-offset data, top
+  var dest-addr/edx: (addr value) <- index data, dest-offset
+  var dest-addr2/eax: (addr handle array value) <- get dest-addr, array-data
+  copy-handle val, dest-addr2
+  # update type
+  var dest-addr3/eax: (addr int) <- get dest-addr, type
+  copy-to *dest-addr3, 2/array
+  increment *top-addr
+}
+
+fn push-value-stack _self: (addr value-stack), val: (addr value) {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  var data-ah/edx: (addr handle array value) <- get self, data
+  var data/eax: (addr array value) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-offset/edx: (offset value) <- compute-offset data, top
+  var dest-addr/edx: (addr value) <- index data, dest-offset
+  copy-object val, dest-addr
+  increment *top-addr
+}
+
+fn pop-number-from-value-stack _self: (addr value-stack) -> _/xmm0: float {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/ecx: (addr int) <- get self, top
+  {
+    compare *top-addr, 0
+    break-if->
+    var minus-one/eax: int <- copy -1
+    var minus-one-f/xmm0: float <- convert minus-one
+    return minus-one-f
+  }
+  decrement *top-addr
+  var data-ah/edx: (addr handle array value) <- get self, data
+  var data/eax: (addr array value) <- lookup *data-ah
+  var top/edx: int <- copy *top-addr
+  var dest-offset/edx: (offset value) <- compute-offset data, top
+  var result-addr/eax: (addr value) <- index data, dest-offset
+  var result-addr2/eax: (addr float) <- get result-addr, number-data
+  return *result-addr2
+}
+
+fn value-stack-empty? _self: (addr value-stack) -> _/eax: boolean {
+  var self/esi: (addr value-stack) <- copy _self
+  var top/eax: (addr int) <- get self, top
+  compare *top, 0
+  {
+    break-if-!=
+    return 1/true
+  }
+  return 0/false
+}
+
+fn value-stack-length _self: (addr value-stack) -> _/eax: int {
+  var self/esi: (addr value-stack) <- copy _self
+  var top-addr/eax: (addr int) <- get self, top
+  return *top-addr
+}
+
+fn save-lines in-h: (handle array (handle array byte)), _out-ah: (addr handle array value) {
+  var _in/eax: (addr array (handle array byte)) <- lookup in-h
+  var in/esi: (addr array (handle array byte)) <- copy _in
+  var len/ecx: int <- length in
+  var out-ah/edi: (addr handle array value) <- copy _out-ah
+  populate out-ah, len
+  var out/eax: (addr array value) <- lookup *out-ah
+  # copy in into out
+  var i/ebx: int <- copy 0
+  {
+    compare i, len
+    break-if->=
+    var src/ecx: (addr handle array byte) <- index in, i
+    var dest-offset/edx: (offset value) <- compute-offset out, i
+    var dest-val/edx: (addr value) <- index out, dest-offset
+    var dest/eax: (addr handle array byte) <- get dest-val, text-data
+    copy-object src, dest
+    var type/edx: (addr int) <- get dest-val, type
+    copy-to *type, 1/string
+    i <- increment
+    loop
+  }
+}
-- 
cgit 1.4.1-2-gfad0