349 lines
9.4 KiB
Lua
349 lines
9.4 KiB
Lua
require("nellie.helper")
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-- CLASS DEFINITIONS
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Expression = class("Expression")
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-- Construct an expression from items (or not)
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function Expression:new(items)
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items = items or {}
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assert_type("table")(items)
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self.items = {}
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for item in iterate(items) do
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self:insert(item)
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end
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end
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-- Return the iterator through the expression
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function Expression:iterate()
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return iterate(self.items)
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end
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-- Is the expression empty?
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function Expression:empty()
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return #self.items == 0
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end
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--[[
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Insert a word or sub expression into this one
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Note: The expression has a .items = {} list.
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]]
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function Expression:insert(...)
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-- closures for nvim highlighting
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local function insert_word(word)
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-- Whitespace might confuse bindings, remove them
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local cleaned = word:match("^%s*(.-)%s*$")
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if cleaned ~= "" then
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table.insert(self.items,cleaned)
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end
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end
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local function insert_expression(expr)
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assert_meta(expr,Expression)
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table.insert(self.items,expr)
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end
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for item in iterate({...}) do
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case_of({
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[Expression] = function(expr)
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insert_expression(expr)
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end,
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string = function(word)
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insert_word(word)
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end
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})(type_of(item),item)
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end
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end
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--[[
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Converts an expression to meaningful text format.
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This should be reparseable.
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]]
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function Expression:string()
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local parts = {}
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for index,item in pairs(self.items) do
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parts[index] = tostring(item)
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end
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return string.format("(%s)",table.concat(parts," "))
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end
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--[[
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Similarly to abstract, returns this expression
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with subexpression:reduce(depth-1)
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Useful for more informative debugging
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]]
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function Expression:reduce(depth)
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local parts = {}
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for index,item in pairs(self.items) do
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parts[index] = case_of({
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[Expression] = function(item)
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if depth == 0 then
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return Expression({"..."})
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else
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return item:reduce(depth - 1)
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end
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end,
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string = id
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})(type_of(item),item)
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end
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end
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--[[
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Returns this expression with all sub expressions
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simplified to text by :text() or '...'
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]]
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function Expression:abstract(infer)
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local parts = {}
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local count = 0
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for index,item in pairs(self.items) do
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parts[index] = case_of({
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[Expression] = function(item)
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local text
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if infer then
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text = item:text()
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if not text then
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count = count + 1
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text = tostring(count)
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end
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else
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text = "..."
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end
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return Expression({text})
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end,
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string = id
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})(type_of(item),item)
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end
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return Expression(parts)
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end
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--[[
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Return the single 'words' part of this expression
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if it is alone. Otherwise return nil.
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]]
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function Expression:text()
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-- Get the text
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local text = self.items[#self.items]
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-- Ensure that the subexpression is valid abstract
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if type(text) ~= "string" then return end
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return text
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end
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--[[
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Give this expression a meaningful debug location
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referring to some source code.
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]]
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function Expression:locate(str,uri)
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self.location = str
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self.source = uri
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return self
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end
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--[[
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Return the meaningful debug location as a string msg.
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]]
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function Expression:link(msg)
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return string.format(
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"in '%s' @%s (%s)",
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msg,
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tostring(self:abstract()),
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tostring(self.location or "?"),
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tostring(self.source or "?.nel")
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)
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end
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Binding = class("Binding")
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-- Construct from a neli string to infer a binding
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-- note that you must wrap this definition in "(<def>)"!
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function Binding:new(expression,callback)
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assert_meta(Expression)(expression,"Arg 'expression' #1: %s")
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if type_of(callback) == "function" then
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self.callback = callback
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else
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self.value = callback
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end
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self.template = expression:abstract(true)
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end
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function Binding:string()
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return string.format("Binding %s: %s",self.template,tostring(self.value or self.callback))
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end
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function Binding:call(s,e,c)
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for item in iterate(e) do
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assert_meta(Expression)(item)
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end
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assert_meta(Scope)(s,"Arg 'scope' #1: %s")
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assert_meta(Chain)(c,"Arg 'chain' #3: %s")
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return self.value or self.callback(s,e,c)
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end
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-- Expecting an abstract expression!
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function Binding:check(expression,candid)
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assert_meta(Expression)(expression,"Arg 'expression' #1: %s")
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candid = candid or expression:abstract()
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assert_meta(Expression)(candid,"Arg 'abstract' #2: %s")
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local data = {}
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local index
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local loop = true
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if #candid.items ~= #self.template.items then
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return false
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end
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while loop do
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local old = index
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index,template_item = next(self.template.items,old)
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index,candid_item = next(candid.items,old)
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local result = case_of({
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[Expression] = function()
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-- item is not an expression, cannot bind
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if type_of(candid_item) ~= Expression then
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loop = false
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else
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local text = template_item:text()
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if not text then
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error(
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string.format(
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[[There was a subexpression without
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just text in this expression: %s]],
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tostring(candid)
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)
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)
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end
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data[text] = expression.items[index]
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assert_meta(Expression)(expression.items[index])
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end
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end,
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string = function()
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-- words don't match, cannot bind
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if candid_item ~= template_item then
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loop = false
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end
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end,
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["nil"] = function()
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-- base case where both expressions terminate together
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if not candid_item then
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return data
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end
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end
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})(type_of(template_item))
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if result then return result end
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end
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end
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Chain = class("Chain")
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function Chain:new(data)
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assert_type("string")(data,"Arg 'data' #1: %s")
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self.data = data
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end
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function Chain:from(previous)
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assert_meta(Chain)(previous,"Arg 'previous' #1: %s")
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previous.next = self
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self.previous = previous
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return self
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end
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function Chain:string()
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return string.format("Chain:%s",table.concat(self:flatten(),", "))
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end
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function Chain:flatten(tab)
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tab = tab or {}
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if self.next then
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self.next:flatten(tab)
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end
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table.insert(tab,self.data)
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return tab
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end
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function Chain:pcall(func)
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local success,result = xpcall(func,function(msg)
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-- If this is a 'nel:' error, strip the line responsible
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-- Otherwise just return the whole traceback since something went really bad
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if not msg then msg = "no message provided" end
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local match = msg:match("nel:%s(.*)")
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if match then
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return match
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else
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return "internal: "..debug.traceback(msg,2)
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end
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end,self)
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if not success then
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log(string.format(
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"nel: %s\nNEL traceback:\n\t%s",
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result,
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table.concat(self:flatten(),"\n\t")
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))
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end
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return success,result
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end
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function Chain:call(func)
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local success,result = self:pcall(func)
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if not success then error("Chain: Halt!") end
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return result
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end
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-- The scope of a neli expression under evaluation
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-- without exact faith to traditional language scopes
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Scope = class("Scope")
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function Scope:new(bindings)
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self.bindings = {}
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for binding in iterate(bindings or {}) do
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self:insert(binding)
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end
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end
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function Scope:string()
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return string.format("Scope: {\n\t%s\n}",table.concat(map(self.bindings,tostring),"\n\t"))
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end
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function Scope:insert(binding)
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assert_meta(Binding)(binding,"Arg 'binding' #1: %s")
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for competitor in iterate(self.bindings) do
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if competitor:check(binding.template) then
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error(
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string.format(
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"nel: Conflicting sibling binding in scope for '%s': '%s'.",
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binding.template,
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competitor.template
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)
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)
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end
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end
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table.insert(self.bindings,binding)
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end
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function Scope:run(expression,chain,original)
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original = original or self
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assert_meta(Expression)(expression,"Arg 'expression' #1: %s")
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assert_meta(Chain)(chain,"Arg 'chain' #2: %s")
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assert_meta(Scope,original,"Arg 'scope' #3: %s")
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-- Could be multiple bindings so make a table
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local binds = {}
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local abstract = expression:abstract()
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for binding in iterate(self.bindings) do
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local bind = binding:check(expression,abstract)
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-- Insert into table
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if bind then binds[binding] = bind end
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end
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local binding,bind = next(binds)
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-- Check for multiple
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if not bind then
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if self.parent then
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return self.parent:run(expression,chain,original)
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else
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local extra = ""
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if #expression.items == 1 then
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local item = expression.items[1]
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if type_of(item) == Expression then
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extra = extra .. "\nNote: This expression is formed (just bracketed) of another single expression. Maybe too many brackets were used here? Are you using curly braces?"
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else
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extra = extra .. "\n\tNote: This is a 'word only' expression, it has no subexpressions. It is most likely that an expected object definition was not bound to the scope or there is a typo."
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end
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end
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error(
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string.format(
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"nel: No binding for '%s' in scope.%s",
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tostring(expression),
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extra
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),3
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)
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end
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-- Should never happen!
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elseif next(binds,binding) then
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local candidates = {}
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for binding,bind in pairs(binds) do
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table.insert(candidates,tostring(binding.template))
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end
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error(
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string.format(
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"nel: Ambiguous bindings in scope for '%s': %s",
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tostring(expression:abstract()),
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table.concat(candidates)
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)
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,2)
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else
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if not binding then error("No binding") end -- todo: improve error
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return binding:call(
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original,
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bind,
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chain
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)
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end
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end |