Add stage 06: Lua bootstrap

The goal of stage 06 is to try parse zig synax in lua. I pulled in
lpeglable 1.2.0 and parser-gen off github to get started. All of this
needs to be cleaned up rather soon.

Lua boostraps using tcc and musl from the previous stage. Since musl
0.6.0 doesn't support dynamic linking this build of lua doesn't support
shared libraries. I couldn't easily patch musl with dlopen and friends
so instead I link statically and call deps with c api.

06/lpeglabel/examples/tiny.lua

@@ -0,0 +1,151 @@
+local re = require 'relabel'
+
+local terror = {}
+
+local function newError(l, msg)
+	table.insert(terror, { l = l, msg = msg} )
+end
+
+newError("errSemi", "Error: missing ';'")  
+newError("errExpIf", "Error: expected expression after 'if'") 
+newError("errThen", "Error: expected 'then' keyword") 
+newError("errCmdSeq1", "Error: expected at least a command after 'then'") 
+newError("errCmdSeq2", "Error: expected at least a command after 'else'") 
+newError("errEnd", "Error: expected 'end' keyword") 
+newError("errCmdSeqRep", "Error: expected at least a command after 'repeat'") 
+newError("errUntil", "Error: expected 'until' keyword") 
+newError("errExpRep", "Error: expected expression after 'until'") 
+newError("errAssignOp", "Error: expected ':=' in assigment") 
+newError("errExpAssign", "Error: expected expression after ':='") 
+newError("errReadName", "Error: expected an identifier after 'read'") 
+newError("errWriteExp", "Error: expected expression after 'write'") 
+newError("errSimpExp", "Error: expected '(', ID, or number after '<' or '='")
+newError("errTerm", "Error: expected '(', ID, or number after '+' or '-'")
+newError("errFactor", "Error: expected '(', ID, or number after '*' or '/'")
+newError("errExpFac", "Error: expected expression after '('")
+newError("errClosePar", "Error: expected ')' after expression")
+
+
+local labelCode = {}
+for k, v in ipairs(terror) do 
+	labelCode[v.l] = k
+end
+
+re.setlabels(labelCode)
+
+local g = re.compile[[
+  Tiny         <- CmdSeq  
+  CmdSeq       <- (Cmd (SEMICOLON / ErrSemi)) (Cmd (SEMICOLON / ErrSemi))*
+  Cmd          <- IfCmd / RepeatCmd / ReadCmd / WriteCmd  / AssignCmd 
+  IfCmd        <- IF (Exp / ErrExpIf)  (THEN / ErrThen)  (CmdSeq / ErrCmdSeq1)  (ELSE (CmdSeq / ErrCmdSeq2)  / '') (END / ErrEnd)
+  RepeatCmd    <- REPEAT  (CmdSeq / ErrCmdSeqRep)  (UNTIL / ErrUntil)  (Exp / ErrExpRep)
+  AssignCmd    <- NAME  (ASSIGNMENT / ErrAssignOp)  (Exp / ErrExpAssign)
+  ReadCmd      <- READ  (NAME / ErrReadName)
+  WriteCmd     <- WRITE  (Exp / ErrWriteExp)
+  Exp          <- SimpleExp  ((LESS / EQUAL) (SimpleExp / ErrSimpExp) / '')
+  SimpleExp    <- Term  ((ADD / SUB)  (Term / ErrTerm))*
+  Term         <- Factor  ((MUL / DIV)  (Factor / ErrFactor))*
+  Factor       <- OPENPAR  (Exp / ErrExpFac)  (CLOSEPAR / ErrClosePar)  / NUMBER  / NAME
+  ErrSemi      <- %{errSemi}
+	ErrExpIf     <- %{errExpIf}
+	ErrThen      <- %{errThen}
+	ErrCmdSeq1   <- %{errCmdSeq1}
+	ErrCmdSeq2   <- %{errCmdSeq2}
+	ErrEnd       <- %{errEnd}
+	ErrCmdSeqRep <- %{errCmdSeqRep}
+	ErrUntil     <- %{errUntil}
+	ErrExpRep    <- %{errExpRep}
+	ErrAssignOp  <- %{errAssignOp}
+	ErrExpAssign <- %{errExpAssign}
+	ErrReadName  <- %{errReadName}
+	ErrWriteExp  <- %{errWriteExp}
+	ErrSimpExp   <- %{errSimpExp}
+	ErrTerm      <- %{errTerm}
+	ErrFactor    <- %{errFactor}
+	ErrExpFac    <- %{errExpFac}
+	ErrClosePar  <- %{errClosePar}
+  ADD          <- Sp '+'
+  ASSIGNMENT   <- Sp ':='
+  CLOSEPAR     <- Sp ')'
+  DIV          <- Sp '/'
+  IF           <- Sp 'if'
+  ELSE         <- Sp 'else'
+  END          <- Sp 'end'
+  EQUAL        <- Sp '='
+  LESS         <- Sp '<'
+  MUL          <- Sp '*'
+  NAME         <- Sp !RESERVED [a-z]+
+  NUMBER       <- Sp [0-9]+
+  OPENPAR      <- Sp '('
+  READ         <- Sp 'read'
+  REPEAT       <- Sp 'repeat'
+  SEMICOLON    <- Sp ';'
+  SUB          <- Sp '-'
+  THEN         <- Sp 'then'
+  UNTIL        <- Sp 'until'
+  WRITE        <- Sp 'write'
+	RESERVED     <- (IF / ELSE / END / READ / REPEAT / THEN / UNTIL / WRITE) ![a-z]+
+  Sp           <- %s*	
+]]
+
+
+local function mymatch(g, s)
+	local r, e, sfail = g:match(s)
+  if not r then
+    local line, col = re.calcline(s, #s - #sfail)
+    local msg = "Error at line " .. line .. " (col " .. col .. "): "
+		return r, msg .. terror[e].msg
+	end 
+	return r
+end
+
+local s = [[
+n := 5;
+f := 1;
+repeat
+  f := f + n;
+  n := n - 1
+until (n < 1);
+write f;]]
+print(mymatch(g, s))
+
+s = [[
+n := 5;
+f := 1;
+repeat
+  f := f + n;
+  n := n - 1;
+until (n < 1);
+read ;]]
+print(mymatch(g, s))
+
+s = [[
+if a < 1 then
+  b := 2;
+else
+  b := 3;]]
+print(mymatch(g, s))
+
+s = [[
+n := 5;
+f := 1;
+repeat
+  f := f + n;
+  n := n - 1;
+untill (n < 1);
+]]
+print(mymatch(g, s))
+
+s = [[
+n := 5;
+f := 1;
+repeat
+  f := f + n;
+  n := n - 1;
+3 (n < 1);
+]]
+print(mymatch(g, s))
+
+print(mymatch(g, "a : 2"))
+print(mymatch(g, "a := (2"))
+