1 files changed, 106 insertions, 0 deletions
diff --git a/piecemeal.lua b/piecemeal.lua
new file mode 100644
index 0000000..0f6dd6c
--- /dev/null
+++ b/piecemeal.lua
@@ -0,0 +1,106 @@
+--[[
+	A parser has the signature: (list, sindex) -> eindex [, output]
+	If the parser "fails", it must return exactly nil.
+	If the parser "succeeds", it must return at least the eindex, and may also return some output.
+]]--
+
+return {
+	lexeme = function (type)
+		return function (l, i)
+			if l[i] and l[i].type == type then
+				return i+1, l[i]
+			end
+			return nil
+		end
+	end,
+	value = function (value)
+		return function (l, i)
+			if l[i] and l[i].value == value then
+				return i+1, l[i]
+			end
+			return nil
+		end
+	end,
+	all = function (...)
+		local args = {...}
+		return function (l, i)
+			local res = {}
+			local eind, out
+			for _, v in ipairs(args) do
+				eind, out = v(l, i)
+				if not eind then return nil end
+				i = eind
+				table.insert(res, out)
+			end
+			return i, res
+		end
+	end,
+	alt = function (...)
+		local args = {...}
+		return function (l, i)
+			local eind, out
+			for _, v in ipairs(args) do
+				eind, out = v(l, i)
+				if eind then
+					return eind, out
+				end
+			end
+			return nil
+		end
+	end,
+	opt = function (p)
+		return function (l, i)
+			local eind, out = p(l, i)
+			if eind
+				then return eind, out
+				else return i
+			end
+		end
+	end,
+	plus = function (p)
+		return function (l, i)
+			local res = {}
+			local eind, out = p(l, i)
+			if not eind then return nil end
+			repeat
+				i = eind
+				table.insert(res, out)
+				eind, out = p(l, i)
+			until not eind
+			return i, res
+		end
+	end,
+	star = function (p)
+		return function (l, i)
+			local res = {}
+			local eind, out
+			repeat
+				eind, out = p(l, i)
+				if eind then
+					table.insert(res, out)
+					i = eind
+				end
+			until not eind
+			return i, res
+		end
+	end,
+
+	postp = function (p, f)
+		return function (l, i)
+			local eind, out = p(l, i)
+			if out then out = f(out) end
+			return eind, out
+		end
+	end,
+
+	parse = function (text, lexer, parser)
+		local tokens = {}
+		lexer:reset(text)
+		local next
+		repeat
+			next = lexer:next()
+			if next then table.insert(tokens, next) end
+		until next == nil
+		return parser(tokens, 1)
+	end,
+}