Printing hello world

1 files changed, 30 insertions, 6 deletions

diff --git a/kernel/main.dats b/kernel/main.dats
index 1eb7813..e7a68f5 100644
--- a/kernel/main.dats
+++ b/kernel/main.dats
@@ -1,13 +1,37 @@
 #include "share/atspre_staload.hats"
 
-typedef test = @{test2 = uint8}
+%{^
+  #define get_vram(_) ((void *) 0xB8000 + 1988)
+%}
+
+typedef cell = @{ ch = char, attrib = uint8 }
+
+extern fun get_vram {n: nat} (n : size_t n):<> [l: agz] (@[cell][n] @ l | ptr l) = "mac#"
+
+extern prfun eat_vram {l: agz} {n: int} (pf: @[cell][n] @ l): void
 
 extern castfn uint8_of {n: nat} (i: int n): uint8 n
 
-implement main0 () = 
-let 
-  val t = @{test2 = uint8_of(4)} : test
-in 
-  main0 ()
+fn string_length {n:nat} (str: string (n)) : size_t (n) = let
+  fun loop {i:nat | i <= n} .<n-i>. (str: string n, i: size_t i): size_t (n) =
+    if string_isnot_atend (str, i) then loop (str, succ(i)) else i
+in
+  loop (str, i2sz(0))
+end
+
+implement main0 () = let
+  val hello = "Hello world!"
+  val length = string_length hello
+  val color_byte = 0x1f
+  val (pf_vram | vram) = get_vram(length)
+  fun loop {l : agz} {n,i: nat | i <= n} .<n-i>. (pf: !(@[cell][n] @ l) | n : size_t n, i : int i, p : ptr l, str: string (n)) : void = 
+    if n > i then (
+      p->[i] := @{ ch = str[i], attrib = uint8_of color_byte };
+      loop(pf | n,i+1,p,str))
+    else ()
+
+in
+  loop(pf_vram | length, 0, vram, hello);
+  let prval () = eat_vram pf_vram in () end
 end