7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 97 insertions, 0 deletions

diff --git a/linux/advent2020/1a.mu b/linux/advent2020/1a.mu
new file mode 100644
index 00000000..67fdc358
--- /dev/null
+++ b/linux/advent2020/1a.mu
@@ -0,0 +1,97 @@
+# https://adventofcode.com/2020/day/1
+#
+# To run (on Linux):
+#   $ git clone https://github.com/akkartik/mu
+#   $ cd mu
+#   $ ./translate_mu apps/advent2020/1a.mu
+#   $ ./a.elf < input
+#   found
+#   1353 667
+#   902451
+#
+# You'll need to register to download the 'input' file for yourself.
+
+fn main -> _/ebx: int {
+  # data structure
+  var numbers-storage: (array int 0x100)  # 256 ints
+  var numbers/esi: (addr array int) <- address numbers-storage
+  var numbers-index/ecx: int <- copy 0
+  # phase 1: parse each line from stdin and add it to numbers
+  {
+    var line-storage: (stream byte 0x100)  # 256 bytes
+    var line/edx: (addr stream byte) <- address line-storage
+    {
+#?       print-string 0, "== iter\n"
+      # read line from stdin
+      clear-stream line
+      read-line-from-real-keyboard line
+      # if line is empty (not even a newline), quit
+      var done?/eax: boolean <- stream-empty? line
+      compare done?, 0/false
+      break-if-!=
+#?       print-stream-to-real-screen line
+      # convert line to int and append it to numbers
+      var n/eax: int <- parse-decimal-int-from-stream line
+#?       print-int32-decimal 0, n
+#?       print-string 0, "\n"
+      var dest/ebx: (addr int) <- index numbers, numbers-index
+      copy-to *dest, n
+      numbers-index <- increment
+#?       print-string 0, "== "
+#?       print-int32-decimal 0, numbers-index
+#?       print-string 0, "\n"
+      loop
+    }
+  }
+  # phase 2: for each number in the array, check if 2020-it is in the rest of
+  # the array
+  var i/eax: int <- copy 0
+  {
+    compare i, numbers-index
+    break-if->=
+    var src/ebx: (addr int) <- index numbers, i
+#?     print-int32-decimal 0, *src
+#?     print-string 0, "\n"
+    var target/ecx: int <- copy 0x7e4  # 2020
+    target <- subtract *src
+    {
+      var found?/eax: boolean <- find-after numbers, i, target
+      compare found?, 0/false
+      break-if-=
+      print-string 0, "found\n"
+      print-int32-decimal 0, *src
+      print-string 0, " "
+      print-int32-decimal 0, target
+      print-string 0, "\n"
+      target <- multiply *src
+      print-int32-decimal 0, target
+      print-string 0, "\n"
+      return 0/success
+    }
+    i <- increment
+    loop
+  }
+  return 1/not-found
+}
+
+fn find-after _numbers: (addr array int), start: int, _target: int -> _/eax: boolean {
+  var numbers/esi: (addr array int) <- copy _numbers
+  var target/edi: int <- copy _target
+  var len/ecx: int <- length numbers
+  var i/eax: int <- copy start
+  i <- increment
+  {
+    compare i, len
+    break-if->=
+    var src/edx: (addr int) <- index numbers, i
+    # if *src == target, return true
+    compare *src, target
+    {
+      break-if-!=
+      return 1/true
+    }
+    i <- increment
+    loop
+  }
+  return 0/false
+}