conditions memoization

doc/luasnip.txt

@@ -1,4 +1,4 @@
-*luasnip.txt*          For NVIM v0.5.0          Last change: 2022 September 15
+*luasnip.txt*          For NVIM v0.5.0          Last change: 2022 September 19
 
 ==============================================================================
 Table of Contents                                  *luasnip-table-of-contents*

lua/luasnip/extras/expand_conditions.lua

@@ -1,13 +1,89 @@
 local M = {}
 
-function M.line_begin(line_to_cursor, matched_trigger)
+-----------------------
+-- CONDITION OBJECTS --
+-----------------------
+local memoization_mt = {
+	-- logic operators
+	-- not
+	__unm = function(o1)
+		return function(...)
+			return not o1(...)
+		end
+	end,
+	-- or
+	__add = function(o1, o2)
+		return function(...)
+			return o1(...) or o2(...)
+		end
+	end,
+	-- and
+	__mul = function(o1, o2)
+		return function(...)
+			return o1(...) and o2(...)
+		end
+	end,
+	-- xnor
+	__eq = function(o1, o2)
+		return function(...)
+			return o1(...) == o2(...)
+		end
+	end,
+	-- use table like a function by overloading __call
+	__call = function(tab, line_to_cursor, matched_trigger, captures)
+		if
+			not tab.mem
+			or tab.invalidate(tab, line_to_cursor, matched_trigger, captures)
+		then
+			tab.mem = tab.func(line_to_cursor, matched_trigger, captures)
+		end
+		return tab.mem
+	end,
+}
+-- low level factory
+-- invalidate(table) -> bool: decides if the memoization should be invalidated,
+-- can store state in table
+function M.memoization_factory(func, invalidate)
+	-- always invalidare by default
+	invalidate = invalidate or function()
+		return true
+	end
+	return setmetatable(
+		{ func = func, invalidate = invalidate },
+		memoization_mt
+	)
+end
+
+-------------------
+-- INVAL PRESETS --
+-------------------
+-- TODO provide invalidate defaults (buffer, cursor, changes, none)
+M.inval = {}
+-- just a small example to illustrate the usage (will most probably have to be
+-- changed)
+function M.inval.line(tab, _, _, _, line)
+	return tab.line ~= line
+end
+
+------------------
+-- COND PRESETS --
+------------------
+local function line_begin(line_to_cursor, matched_trigger)
 	-- +1 because `string.sub("abcd", 1, -2)` -> abc
 	return line_to_cursor:sub(1, -(#matched_trigger + 1)):match("^%s*$")
 end
+function M.line_begin()
+	-- TODO invalidation function
+	return M.memoization_factory(line_begin, nil)
+end
 
-function M.line_end(line_to_cursor)
+local function line_end(line_to_cursor)
 	local line = vim.api.nvim_get_current_line()
 	return #line_to_cursor == #line
 end
+function M.line_end()
+	-- TODO invalidation function
+	return M.memoization_factory(line_end, nil)
+end
 
 return M