🔖 is now a function reference

LANGUAGE.md

@@ -248,7 +248,7 @@ Functions can return a value using a [return line](#lines-that-can-t-have-childr
 Functions always have the following variables defined in its namespace by default:
 
 `👁️`: number, number of times the function was executed before
-`🔖`: string, name of last reached checkpoint
+`🔖`: funcion reference, last reached checkpoint. `nil` if no checkpoint reached.
 
 * `§`: checkpoint. Followed by an [identifier](#identifiers), then eventually an [alias](#aliases). Define a checkpoint. Also define a new namespace for its children.
 

interpreter/expression.lua

@@ -437,11 +437,11 @@ local function eval(state, exp)
 				else
 					local e
 					-- eval function from start
-					if paren_call or checkpoint.value == "" then
+					if paren_call or checkpoint.type == "nil" then
 						ret, e = run(state, fn.child)
 					-- resume at last checkpoint
 					else
-						local expr, err = expression(checkpoint.value, state, fn.namespace)
+						local expr, err = expression(checkpoint.value[1], state, fn.namespace)
 						if not expr then return expr, err end
 						ret, e = eval(state, expr)
 					end

interpreter/interpreter.lua

@@ -116,8 +116,8 @@ run_line = function(state, line)
 			value = reached.value + 1
 		})
 		set_variable(state, line.parent_function.namespace.."🔖", {
-			type = "string",
-			value = line.name
+			type = "function reference",
+			value = { line.name }
 		})
 		merge_state(state)
 	else
@@ -167,11 +167,10 @@ run_block = function(state, block, resume_from_there, i, j)
 		})
 		-- don't update checkpoint if an already more precise checkpoint is set
 		-- (since we will go up the whole checkpoint hierarchy when resuming from a nested checkpoint)
-		local current_checkpoint = checkpoint.value
-		if not current_checkpoint:match("^"..escape(parent_line.name)) then
+		if checkpoint.type == "nil" or not checkpoint.value[1]:match("^"..escape(parent_line.name)) then
 			set_variable(state, parent_line.parent_function.namespace.."🔖", {
-				type = "string",
-				value = parent_line.name
+				type = "function reference",
+				value = { parent_line.name }
 			})
 		end
 		merge_state(state)

parser/preparser.lua

@@ -191,9 +191,9 @@ local function parse_line(line, state, namespace)
 			-- define 🔖 variable
 			local checkpoint_alias = state.global_state.builtin_aliases["🔖"]
 			if checkpoint_alias then
-				table.insert(line.children, 1, { content = (":🔖:%s=\"\""):format(checkpoint_alias), source = line.source })
+				table.insert(line.children, 1, { content = (":🔖:%s=()"):format(checkpoint_alias), source = line.source })
 			else
-				table.insert(line.children, 1, { content = ":🔖=\"\"", source = line.source })
+				table.insert(line.children, 1, { content = ":🔖=()", source = line.source })
 			end
 		elseif r.type == "checkpoint" then
 			-- define 🏁 variable

test/tests/checkpoint change.ans

@@ -29,5 +29,5 @@ From q again:
 ~ f
 
 Go to p again by setting checkpoint manually:
-~ f.checkpoint := "p"
+~ f.checkpoint := &f.p
 ~ f