rjpcomputing/luaforwindows
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
luaforwindows/files/lua/metalua/ast_to_string.mlua

554 lines
17 KiB
Plaintext
Executable File
Raw Blame History

-{ extension 'match' }
local M = { }
M.__index = M
ast_to_string = |x| M.run(x)
--------------------------------------------------------------------------------
-- Instanciate a new AST->source synthetizer
--------------------------------------------------------------------------------
function M.new ()
local self = {
_acc = { }, -- Accumulates pieces of source as strings
current_indent = 0, -- Current level of line indentation
indent_step = " " -- Indentation symbol, normally spaces or '\t'
}
return setmetatable (self, M)
end
--------------------------------------------------------------------------------
-- Run a synthetizer on the `ast' arg and return the source as a string.
-- Can also be used as a static method `M.run (ast)'; in this case,
-- a temporary Metizer is instanciated on the fly.
--------------------------------------------------------------------------------
function M:run (ast)
if not ast then
self, ast = M.new(), self
end
self._acc = { }
self:node (ast)
return table.concat (self._acc)
end
--------------------------------------------------------------------------------
-- Accumulate a piece of source file in the synthetizer.
--------------------------------------------------------------------------------
function M:acc (x)
if x then table.insert (self._acc, x) end
end
--------------------------------------------------------------------------------
-- Accumulate an indented newline.
-- Jumps an extra line if indentation is 0, so that
-- toplevel definitions are separated by an extra empty line.
--------------------------------------------------------------------------------
function M:nl ()
if self.current_indent == 0 then self:acc "\n" end
self:acc ("\n" .. self.indent_step:rep (self.current_indent))
end
--------------------------------------------------------------------------------
-- Increase indentation and accumulate a new line.
--------------------------------------------------------------------------------
function M:nlindent ()
self.current_indent = self.current_indent + 1
self:nl ()
end
--------------------------------------------------------------------------------
-- Decrease indentation and accumulate a new line.
--------------------------------------------------------------------------------
function M:nldedent ()
self.current_indent = self.current_indent - 1
self:acc ("\n" .. self.indent_step:rep (self.current_indent))
end
--------------------------------------------------------------------------------
-- Keywords, which are illegal as identifiers.
--------------------------------------------------------------------------------
local keywords = table.transpose {
"and", "break", "do", "else", "elseif",
"end", "false", "for", "function", "if",
"in", "local", "nil", "not", "or",
"repeat", "return", "then", "true", "until",
"while" }
--------------------------------------------------------------------------------
-- Return true iff string `id' is a legal identifier name.
--------------------------------------------------------------------------------
local function is_ident (id)
return id:strmatch "^[%a_][%w_]*$" and not keywords[id]
end
--------------------------------------------------------------------------------
-- Return true iff ast represents a legal function name for
-- syntax sugar ``function foo.bar.gnat() ... end'':
-- a series of nested string indexes, with an identifier as
-- the innermost node.
--------------------------------------------------------------------------------
local function is_idx_stack (ast)
match ast with
| `Id{ _ } -> return true
| `Index{ left, `String{ _ } } -> return is_idx_stack (left)
| _ -> return false
end
end
--------------------------------------------------------------------------------
-- Operator precedences, in increasing order.
-- This is not directly used, it's used to generate op_prec below.
--------------------------------------------------------------------------------
local op_preprec = {
{ "or", "and" },
{ "lt", "le", "eq", "ne" },
{ "concat" },
{ "add", "sub" },
{ "mul", "div", "mod" },
{ "unary", "not", "len" },
{ "pow" },
{ "index" } }
--------------------------------------------------------------------------------
-- operator --> precedence table, generated from op_preprec.
--------------------------------------------------------------------------------
local op_prec = { }
for prec, ops in ipairs (op_preprec) do
for op in ivalues (ops) do
op_prec[op] = prec
end
end
--------------------------------------------------------------------------------
-- operator --> source representation.
--------------------------------------------------------------------------------
local op_symbol = {
add = " + ", sub = " - ", mul = " * ",
div = " / ", mod = " % ", pow = " ^ ",
concat = " .. ", eq = " == ", ne = " ~= ",
lt = " < ", le = " <= ", ["and"] = " and ",
["or"] = " or ", ["not"] = "not ", len = "# " }
--------------------------------------------------------------------------------
-- Accumulate the source representation of AST `node' in
-- the synthetizer. Most of the work is done by delegating to
-- the method having the name of the AST tag.
-- If something can't be converted to normal sources, it's
-- instead dumped as a `-{ ... }' splice in the source accumulator.
--------------------------------------------------------------------------------
function M:node (node)
assert (self~=M and self._acc)
if not node.tag then -- tagless block.
self:list (node, self.nl)
else
local f = M[node.tag]
if type (f) == "function" then -- Delegate to tag method.
f (self, node, unpack (node))
elseif type (f) == "string" then -- tag string.
self:acc (f)
else -- No appropriate method, fall back to splice dumping.
-- This cannot happen in a plain Lua AST.
self:acc " -{ "
self:acc (table.tostring (node, "nohash"), 80)
self:acc " }"
end
end
end
--------------------------------------------------------------------------------
-- Convert every node in the AST list `list' passed as 1st arg.
-- `sep' is an optional separator to be accumulated between each list element,
-- it can be a string or a synth method.
-- `start' is an optional number (default == 1), indicating which is the
-- first element of list to be converted, so that we can skip the begining
-- of a list.
--------------------------------------------------------------------------------
function M:list (list, sep, start)
for i = start or 1, # list do
self:node (list[i])
if list[i + 1] then
if not sep then
elseif type (sep) == "function" then sep (self)
elseif type (sep) == "string" then self:acc (sep)
else error "Invalid list separator" end
end
end
end
--------------------------------------------------------------------------------
--
-- Tag methods.
-- ------------
--
-- Specific AST node dumping methods, associated to their node kinds
-- by their name, which is the corresponding AST tag.
-- synth:node() is in charge of delegating a node's treatment to the
-- appropriate tag method.
--
-- Such tag methods are called with the AST node as 1st arg.
-- As a convenience, the n node's children are passed as args #2 ... n+1.
--
-- There are several things that could be refactored into common subroutines
-- here: statement blocks dumping, function dumping...
-- However, given their small size and linear execution
-- (they basically perform series of :acc(), :node(), :list(),
-- :nl(), :nlindent() and :nldedent() calls), it seems more readable
-- to avoid multiplication of such tiny functions.
--
-- To make sense out of these, you need to know metalua's AST syntax, as
-- found in the reference manual or in metalua/doc/ast.txt.
--
--------------------------------------------------------------------------------
function M:Do (node)
self:acc "do"
self:nlindent ()
self:list (node, self.nl)
self:nldedent ()
self:acc "end"
end
function M:Set (node)
match node with
| `Set{ { `Index{ lhs, `String{ method } } },
{ `Function{ { `Id "self", ... } == params, body } } }
if is_idx_stack (lhs) and is_ident (method) ->
-- ``function foo:bar(...) ... end'' --
self:acc "function "
self:node (lhs)
self:acc ":"
self:acc (method)
self:acc " ("
self:list (params, ", ", 2)
self:acc ")"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
| `Set{ { lhs }, { `Function{ params, body } } } if is_idx_stack (lhs) ->
-- ``function foo(...) ... end'' --
self:acc "function "
self:node (lhs)
self:acc " ("
self:list (params, ", ")
self:acc ")"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
| `Set{ { `Id{ lhs1name } == lhs1, ... } == lhs, rhs }
if not is_ident (lhs1name) ->
-- ``foo, ... = ...'' when foo is *not* a valid identifier.
-- In that case, the spliced 1st variable must get parentheses,
-- to be distinguished from a statement splice.
-- This cannot happen in a plain Lua AST.
self:acc "("
self:node (lhs1)
self:acc ")"
if lhs[2] then -- more than one lhs variable
self:acc ", "
self:list (lhs, ", ", 2)
end
self:acc " = "
self:list (rhs, ", ")
| `Set{ lhs, rhs } ->
-- ``... = ...'', no syntax sugar --
self:list (lhs, ", ")
self:acc " = "
self:list (rhs, ", ")
end
end
function M:While (node, cond, body)
self:acc "while "
self:node (cond)
self:acc " do"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
end
function M:Repeat (node, body, cond)
self:acc "repeat"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "until "
self:node (cond)
end
function M:If (node)
for i = 1, #node-1, 2 do
-- for each ``if/then'' and ``elseif/then'' pair --
local cond, body = node[i], node[i+1]
self:acc (i==1 and "if " or "elseif ")
self:node (cond)
self:acc " then"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
end
-- odd number of children --> last one is an `else' clause --
if #node%2 == 1 then
self:acc "else"
self:nlindent ()
self:list (node[#node], self.nl)
self:nldedent ()
end
self:acc "end"
end
function M:Fornum (node, var, first, last)
local body = node[#node]
self:acc "for "
self:node (var)
self:acc " = "
self:node (first)
self:acc ", "
self:node (last)
if #node==5 then -- 5 children --> child #4 is a step increment.
self:acc ", "
self:node (node[4])
end
self:acc " do"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
end
function M:Forin (node, vars, generators, body)
self:acc "for "
self:list (vars, ", ")
self:acc " in "
self:list (generators, ", ")
self:acc " do"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
end
function M:Local (node, lhs, rhs)
if next (lhs) then
self:acc "local "
self:list (lhs, ", ")
if rhs[1] then
self:acc " = "
self:list (rhs, ", ")
end
else -- Can't create a local statement with 0 variables in plain Lua
self:acc (table.tostring (node, 'nohash', 80))
end
end
function M:Localrec (node, lhs, rhs)
match node with
| `Localrec{ { `Id{name} }, { `Function{ params, body } } }
if is_ident (name) ->
-- ``local function name() ... end'' --
self:acc "local function "
self:acc (name)
self:acc " ("
self:list (params, ", ")
self:acc ")"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
| _ ->
-- Other localrec are unprintable ==> splice them --
-- This cannot happen in a plain Lua AST. --
self:acc "-{ "
self:acc (table.tostring (node, 'nohash', 80))
self:acc " }"
end
end
function M:Call (node, f)
-- single string or table literal arg ==> no need for parentheses. --
local parens
match node with
| `Call{ _, `String{_} }
| `Call{ _, `Table{...}} -> parens = false
| _ -> parens = true
end
self:node (f)
self:acc (parens and " (" or " ")
self:list (node, ", ", 2) -- skip `f'.
self:acc (parens and ")")
end
function M:Invoke (node, f, method)
-- single string or table literal arg ==> no need for parentheses. --
local parens
match node with
| `Invoke{ _, _, `String{_} }
| `Invoke{ _, _, `Table{...}} -> parens = false
| _ -> parens = true
end
self:node (f)
self:acc ":"
self:acc (method[1])
self:acc (parens and " (" or " ")
self:list (node, ", ", 3) -- Skip args #1 and #2, object and method name.
self:acc (parens and ")")
end
function M:Return (node)
self:acc "return "
self:list (node, ", ")
end
M.Break = "break"
M.Nil = "nil"
M.False = "false"
M.True = "true"
M.Dots = "..."
function M:Number (node, n)
self:acc (tostring (n))
end
function M:String (node, str)
-- format "%q" prints '\n' in an umpractical way IMO,
-- so this is fixed with the :gsub( ) call.
self:acc (string.format ("%q", str):gsub ("\\\n", "\\n"))
end
function M:Function (node, params, body)
self:acc "function ("
self:list (params, ", ")
self:acc ")"
self:nlindent ()
self:list (body, self.nl)
self:nldedent ()
self:acc "end"
end
function M:Table (node)
if not node[1] then self:acc "{ }" else
self:acc "{"
if #node > 1 then self:nlindent () else self:acc " " end
for i, elem in ipairs (node) do
match elem with
| `Pair{ `String{ key }, value } if is_ident (key) ->
-- ``key = value''. --
self:acc (key)
self:acc " = "
self:node (value)
| `Pair{ key, value } ->
-- ``[key] = value''. --
self:acc "["
self:node (key)
self:acc "] = "
self:node (value)
| _ ->
-- ``value''. --
self:node (elem)
end
if node [i+1] then
self:acc ","
self:nl ()
end
end
if #node > 1 then self:nldedent () else self:acc " " end
self:acc "}"
end
end
function M:Op (node, op, a, b)
-- Transform ``not (a == b)'' into ``a ~= b''. --
match node with
| `Op{ "not", `Op{ "eq", _a, _b } }
| `Op{ "not", `Paren{ `Op{ "eq", _a, _b } } } ->
op, a, b = "ne", _a, _b
| _ ->
end
if b then -- binary operator.
local left_paren, right_paren
match a with
| `Op{ op_a, ...} if op_prec[op] >= op_prec[op_a] -> left_paren = true
| _ -> left_paren = false
end
match b with -- FIXME: might not work with right assoc operators ^ and ..
| `Op{ op_b, ...} if op_prec[op] >= op_prec[op_b] -> right_paren = true
| _ -> right_paren = false
end
self:acc (left_paren and "(")
self:node (a)
self:acc (left_paren and ")")
self:acc (op_symbol [op])
self:acc (right_paren and "(")
self:node (b)
self:acc (right_paren and ")")
else -- unary operator.
local paren
match a with
| `Op{ op_a, ... } if op_prec[op] >= op_prec[op_a] -> paren = true
| _ -> paren = false
end
self:acc (op_symbol[op])
self:acc (paren and "(")
self:node (a)
self:acc (paren and ")")
end
end
function M:Paren (node, content)
self:acc "("
self:node (content)
self:acc ")"
end
function M:Index (node, table, key)
local paren_table
-- Check precedence, see if parens are needed around the table --
match table with
| `Op{ op, ... } if op_prec[op] < op_prec.index -> paren_table = true
| _ -> paren_table = false
end
self:acc (paren_table and "(")
self:node (table)
self:acc (paren_table and ")")
match key with
| `String{ field } if is_ident (field) ->
-- ``table.key''. --
self:acc "."
self:acc (field)
| _ ->
-- ``table [key]''. --
self:acc "["
self:node (key)
self:acc "]"
end
end
function M:Id (node, name)
if is_ident (name) then
self:acc (name)
else -- Unprintable identifier, fall back to splice representation.
-- This cannot happen in a plain Lua AST.
self:acc "-{`Id "
self:String (node, name)
self:acc "}"
end
end
Reference in New Issue View Git Blame Copy Permalink