#region data
	global.LOG_EXPRESSION = false;
	
	global.EVALUATE_HEAD = noone;

	global.EQUATION_PRES = ds_map_create();
	global.EQUATION_PRES[? "+"] = 1;
	global.EQUATION_PRES[? "-"] = 1;
	global.EQUATION_PRES[? "∸"] = 9; //unary negative
	global.EQUATION_PRES[? "*"] = 2;
	global.EQUATION_PRES[? "/"] = 2;
	global.EQUATION_PRES[? "%"] = 2;
	global.EQUATION_PRES[? "$"] = 3;
	
	global.EQUATION_PRES[? "&"] = 5;
	global.EQUATION_PRES[? "|"] = 4;
	global.EQUATION_PRES[? "^"] = 3;
	global.EQUATION_PRES[? "<"] = 3;
	global.EQUATION_PRES[? "»"] = 6;
	global.EQUATION_PRES[? "«"] = 6;
	global.EQUATION_PRES[? "~"] = 9;
	
	global.EQUATION_PRES[? "="]  = -99;
	global.EQUATION_PRES[? "⊕"]  = -99; //+=
	global.EQUATION_PRES[? "⊖"]  = -99; //-=
	global.EQUATION_PRES[? "⊗"]  = -99; //*=
	global.EQUATION_PRES[? "⊘"]  = -99; ///=
	
	global.EQUATION_PRES[? "⩵"] = -1; //==
	global.EQUATION_PRES[? "≠"]  = -1; //!=
	global.EQUATION_PRES[? "<"]  =  0;
	global.EQUATION_PRES[? ">"]  =  0;
	global.EQUATION_PRES[? "≤"]  =  0;
	global.EQUATION_PRES[? "≥"]  =  0;
	
	global.EQUATION_PRES[? "@"] = 5; //array accerssor symbol
	
	global.FUNCTIONS    = ds_map_create();
	global.FUNCTIONS[? "sin"]    = [ ["radian"], function(val) { return sin(val[0]); } ];
	global.FUNCTIONS[? "cos"]    = [ ["radian"], function(val) { return cos(val[0]); } ];
	global.FUNCTIONS[? "tan"]    = [ ["radian"], function(val) { return tan(val[0]); } ];
	
	global.FUNCTIONS[? "abs"]    = [ ["number"], function(val) { return abs(val[0]); } ];
	global.FUNCTIONS[? "round"]  = [ ["number"], function(val) { return round(val[0]); } ];
	global.FUNCTIONS[? "ceil"]   = [ ["number"], function(val) { return ceil(val[0]);  } ];
	global.FUNCTIONS[? "floor"]  = [ ["number"], function(val) { return floor(val[0]); } ];
	
	global.FUNCTIONS[? "lerp"]   = [ ["number_0", "number_1", "amount"], function(val) { return lerp(array_safe_get(val, 0), array_safe_get(val, 1), array_safe_get(val, 2)); } ];
	
	global.FUNCTIONS[? "wiggle"] = [ ["time", "frequency", "octave = 1", "seed = 0"],	function(val) { 
																								return wiggle(0, 1, PROJECT.animator.frameTotal / array_safe_get(val, 1), 
																												array_safe_get(val, 0), 
																												array_safe_get(val, 3, 0), 
																												array_safe_get(val, 2, 1)); 
																						} ];
	global.FUNCTIONS[? "random"] = [ ["min = 0", "max = 1"],	function(val) { 
																	return random_range(array_safe_get(val, 0, 0), 
																					    array_safe_get(val, 1, 1)); 
																} ];
	global.FUNCTIONS[? "irandom"] = [ ["min = 0", "max = 1"],	function(val) { 
																	return irandom_range(array_safe_get(val, 0, 0), 
																					     array_safe_get(val, 1, 1)); 
																} ];
	
	global.FUNCTIONS[? "range"] = [ ["length", "start = 0", "step = 1"],	function(val) { 
																				var arr = array_create(array_safe_get(val, 0, 0));
																				for( var i = 0, n = array_length(arr); i < n; i++ ) 
																					arr[i] = array_safe_get(val, 1, 0) + i * array_safe_get(val, 2, 1);
																				return arr;
																			} ];
	
	globalvar PROJECT_VARIABLES;
	PROJECT_VARIABLES = {};
	
	PROJECT_VARIABLES.Project = {};
	PROJECT_VARIABLES.Project.frame			= function() /*=>*/ {return PROJECT.animator.current_frame};
	PROJECT_VARIABLES.Project.progress		= function() /*=>*/ {return PROJECT.animator.current_frame / (PROJECT.animator.frames_total - 1)};
	PROJECT_VARIABLES.Project.frameTotal	= function() /*=>*/ {return PROJECT.animator.frames_total};
	PROJECT_VARIABLES.Project.fps			= function() /*=>*/ {return PROJECT.animator.framerate};
	PROJECT_VARIABLES.Project.time			= function() /*=>*/ {return PROJECT.animator.current_frame / PROJECT.animator.framerate};
	PROJECT_VARIABLES.Project.name			= function() /*=>*/ {return filename_name_only(PROJECT.path)};
	
	PROJECT_VARIABLES.Program = {};
	PROJECT_VARIABLES.Program.time			= function() /*=>*/ {return current_time / 1000};
	
	PROJECT_VARIABLES.Device = {};
	PROJECT_VARIABLES.Device.timeSecond			= function() /*=>*/ {return current_second};
	PROJECT_VARIABLES.Device.timeMinute			= function() /*=>*/ {return current_minute};
	PROJECT_VARIABLES.Device.timeHour			= function() /*=>*/ {return current_hour};
	PROJECT_VARIABLES.Device.timeDay			= function() /*=>*/ {return current_day};
	PROJECT_VARIABLES.Device.timeDayInWeek		= function() /*=>*/ {return current_weekday};
	PROJECT_VARIABLES.Device.timeMonth			= function() /*=>*/ {return current_month};
	PROJECT_VARIABLES.Device.timeYear			= function() /*=>*/ {return current_year};
#endregion

function functionStringClean(fx) {
	var ch = "", ind = 0, len = string_length(fx);
	var _fx = "", str = false;
	while(ind++ <= len) {
		ch = string_char_at(fx, ind);
		
		if(ch == " ") {
			if(str)
				_fx += ch;
		} else
			_fx += ch;
			
		if(ch == "\"")
			str = !str;
	}
	
	fx = _fx;
	
	
	fx = string_replace_all(fx, "\n", "");
	fx = string_replace_all(fx, "**", "$");
	fx = string_replace_all(fx, "<<", "«");
	fx = string_replace_all(fx, ">>", "»");
	
	fx = string_replace_all(fx, "==", "⩵");
	fx = string_replace_all(fx, "!=", "≠");
	fx = string_replace_all(fx, "<>", "≠");
	fx = string_replace_all(fx, ">=", "≥");
	fx = string_replace_all(fx, "<=", "≤");
	
	fx = string_replace_all(fx, "++", "⊕1");
	fx = string_replace_all(fx, "--", "⊖1");
	
	fx = string_replace_all(fx, "+=", "⊕");
	fx = string_replace_all(fx, "-=", "⊖");
	fx = string_replace_all(fx, "*=", "⊗");
	fx = string_replace_all(fx, "/=", "⊘");
	
	fx = string_trim(fx);
	
	return fx;
}

#region evaluator
	enum EXPRESS_TREE_ANIM {
		none,
		base_value,
		animated
	}
	
	function __funcList() constructor {
		funcTrees = [];
		
		static addFunction = function(fn) {
			array_push(funcTrees, fn);
		}
		
		static validate = function() {
			for( var i = 0, n = array_length(funcTrees); i < n; i++ )
				if(!funcTrees[i].validate())
					return false;
				
			return true;
		}
		
		static isAnimated = function() {
			for( var i = 0, n = array_length(funcTrees); i < n; i++ )
				if(!funcTrees[i].isAnimated())
					return false;
				
			return true;
		}
		
		static eval = function(params = {}) {
			//var _params = variable_clone(params);
			var val = 0;
			
			for( var i = 0, n = array_length(funcTrees); i < n; i++ )
				val = funcTrees[i].eval(params);
				
			return val;
		}
	}
	
	function __funcIf() constructor {
		condition = noone;
		if_true   = new __funcList();
		if_false  = new __funcList();
		
		static validate = function() {
			if(condition != noone && !condition.validate())	return false;
			if(if_true != noone && !if_true.validate())		return false;
			if(if_false != noone && !if_false.validate())	return false;
			return true;
		}
		
		static isAnimated = function() {
			if(condition != noone && !condition.isAnimated())	return false;
			if(if_true != noone && !if_true.isAnimated())		return false;
			if(if_false != noone && !if_false.isAnimated())		return false;
			return true;
		}
		
		static eval = function(params = {}) {
			if(condition == noone) return 0;
			
			var res = condition.eval(params);
			printIf(global.LOG_EXPRESSION, $"<<<<<< IF {res} >>>>>>");
			
			if(res) return if_true == noone? 0  : if_true.eval(params);
			else    return if_false == noone? 0 : if_false.eval(params);
		}
	}
	
	function __funcFor() constructor {
		itr_array = false;
		
		cond_init = noone;
		cond_indx = noone;
		cond_iter = noone;
		cond_term = noone;
		
		cond_arr  = noone;
		
		cond_step = 1;
		action    = new __funcList();
		
		static validate = function() {
			if(itr_array) {
				if(cond_arr == noone || !cond_arr.validate()) return false;
			} else {
				if(cond_init == noone || !cond_init.validate()) return false;
				if(cond_term == noone || !cond_term.validate())	return false;
			}
			
			if(action != noone && !action.validate())		return false;
			
			return true;
		}
		
		static isAnimated = function() {
			if(itr_array) {
				if(cond_arr == noone || !cond_arr.isAnimated())	return false;
			} else {
				if(cond_init == noone || !cond_init.isAnimated())	return false;
				if(cond_term == noone || !cond_term.isAnimated())	return false;
			}
			
			if(action != noone && !action.isAnimated())			return false;
			
			return true;
		}
		
		static eval = function(params = {}) {
			if(itr_array) {
				var _arr = cond_arr.eval(params);
				printIf(global.LOG_EXPRESSION, $"<<<<<< FOR EACH {_arr} >>>>>>");
				for( var i = 0, n = array_length(_arr); i < n; i++ ) {
					var val = _arr[i];
					if(cond_indx != noone)
						params[$ cond_indx] = i;
					params[$ cond_iter] = val;
					
					printIf(global.LOG_EXPRESSION, $"<< ITER {i}: {cond_iter} = {val} >>");
					action.eval(params);
				}
			} else {
				printIf(global.LOG_EXPRESSION, "<< FOR >>");
				cond_init.eval(params);
				
				while(cond_term.eval(params)) {
					action.eval(params);
					cond_iter.eval(params);
				}
			}
		}
	}
	
	function __funcTree(symbol, l = noone, r = noone) constructor {
		self.symbol = symbol;
		self.l = l;
		self.r = r;
		dependency = [];
		
		static _string = function(str) {
			return string_char_at(str, 1) == "\"" &&  string_char_at(str, string_length(str)) == "\"";
		}
		
		static _string_trim = function(str) {
			return string_trim(str, [ "\"" ]);
		}
		
		static getVal = function(val, params = {}, getRaw = false) {
			if(is_struct(val))	return val.eval(params, getRaw);
			if(is_real(val))	return val;
			if(getRaw)			return val;
			
			if(is_string(val)) val = string_trim(val);
			
			//printIf(global.LOG_EXPRESSION, $"    [ get struct {params}[{val}] ]");
			
			if(struct_has(params, val))
				return struct_try_get(params, val);
			
			val = string_trim(val);
			
			if(_string(val))
				return _string_trim(val);
			
			return nodeGetData(val);
		}
		
		static _validate = function(val) {
			if(is_real(val))   return true;
			if(is_string(val)) return true;
			if(is_struct(val)) return val.validate();

			if(val == "value") return true;
			if(PROJECT.globalNode.inputExist(val)) return true;
			
			var strs = string_splice(val, ".");
			if(array_length(strs) < 2) return false;
			
			if(struct_has(PROJECT_VARIABLES, strs[0]))
				return struct_has(PROJECT_VARIABLES[$ strs[0]], strs[1]);
			
			if(!ds_map_exists(PROJECT.nodeNameMap, strs[0]))
				return false;
			
			array_push_unique(dependency, strs[0]);
			return true;
		}
		
		static validate = function() {
			dependency = [];
			
			if(ds_map_exists(global.FUNCTIONS, symbol)) {
				if(!is_array(l)) return false;
				for( var i = 0, n = array_length(l); i < n; i++ )
					if(!_validate(l[i])) return false;
				return true;
			}
				
			switch(symbol) {
				case "@": return _validate(l);
				case "【": return true;
				case "":  return true;
			}
			
			return _validate(l) && _validate(r);
		}
		
		static _isAnimated = function(val) {
			if(is_real(val))   return EXPRESS_TREE_ANIM.none;
			if(is_struct(val)) return val._isAnimated();
			
			if(val == "value") return EXPRESS_TREE_ANIM.base_value;
			if(PROJECT.globalNode.inputExist(val)) {
				var _inp = PROJECT.globalNode.getInput(val);
				if(_inp.is_anim) return EXPRESS_TREE_ANIM.animated;
			}
			
			return EXPRESS_TREE_ANIM.none;
		}
		
		static isAnimated = function() {
			var anim = EXPRESS_TREE_ANIM.none;
			anim = max(anim, _isAnimated(l));
			if(symbol != "@")
				anim = max(anim, _isAnimated(r));
			
			return anim;
		}
		
		static eval = function(params = {}, isLeft = false) {
			if(ds_map_exists(global.FUNCTIONS, symbol)) {
				if(!is_array(l)) return 0;
				
				var _fn = global.FUNCTIONS[? symbol];
				var _ev = _fn[1];
				var _l  = array_create(array_length(l));
				
				for( var i = 0, n = array_length(l); i < n; i++ )
					_l[i] = getVal(l[i], params);
					
				var res = _ev(_l);
				printIf(global.LOG_EXPRESSION, $"Function {symbol}{_l} = {res}");
				printIf(global.LOG_EXPRESSION, "====================");
				
				return res;
			}
			
			var getRaw = false;
			switch(symbol) {
				case "=":	
				case "【":	
					getRaw = true;
			}
			
			var v1 = getVal(l, params, getRaw || isLeft);
			var v2 = getVal(r, params);
			
			var res = 0;
			
			if(symbol == "") {
				res = v1;
			} else if(symbol == "【") { //array builder
				res = array_create(array_length(v1));
				for( var i = 0, n = array_length(res); i < n; i++ )
					res[i] = getVal(v1[i], params);
			} else if(symbol == "@") {
				if(isLeft)	res = [ v1, v2 ];
				else		res = is_real(v2)? array_safe_get(v1, v2) : 0;
			} else if(symbol == "=") {
				if(is_array(v1)) { 
					var val = params[$ v1[0]];
					val = array_safe_set(val, v1[1], v2);
					params[$ v1[0]] = val;
					res = val;
				} else {
					params[$ v1] = v2;
					res = v2;
				}
			} else if(is_array(v1) && !is_array(v2)) {
				res = array_create(array_length(v1));
				for( var i = 0, n = array_length(res); i < n; i++ )
					res[i] = eval_real(array_safe_get(v1, i), v2);
			} else if(!is_array(v1) && is_array(v2)) {
				res = array_create(array_length(v2));
				for( var i = 0, n = array_length(res); i < n; i++ )
					res[i] = eval_real(v1, array_safe_get(v2, i));
			} else if(is_array(v1) && is_array(v2)) {
				res = array_create(max(array_length(v1), array_length(v2)));
				for( var i = 0, n = array_length(res); i < n; i++ )
					res[i] = eval_real(array_safe_get(v1, i), array_safe_get(v2, i));
			} else 
				res = eval_real(v1, v2);
			
			var _v1_var = getVal(l, params, true);
			switch(symbol) {
				case "⊕": 
				case "⊖": 
				case "⊗": 
				case "⊘": 
					if(is_array(_v1_var)) { 
						var val = params[$ _v1_var[0]];
						val = array_safe_set(val, _v1_var[1], res);
						params[$ _v1_var[0]] = val;
					} else
						params[$ _v1_var] = res;
				
					printIf(global.LOG_EXPRESSION, $"|{_v1_var}| = {v1}|{symbol}|{v2}| = {res}");
					printIf(global.LOG_EXPRESSION, $"symbol : {symbol}");
					printIf(global.LOG_EXPRESSION, $"l      : | {typeof(l)} |{l}|");
					printIf(global.LOG_EXPRESSION, $"r      : | {typeof(r)} |{r}|");
					printIf(global.LOG_EXPRESSION, "====================");
					break;
				default:
					printIf(global.LOG_EXPRESSION, $"|{v1}|{symbol}|{v2}| = {res}");
					printIf(global.LOG_EXPRESSION, $"symbol : {symbol}");
					printIf(global.LOG_EXPRESSION, $"l      : | {typeof(l)} |{l}|");
					printIf(global.LOG_EXPRESSION, $"r      : | {typeof(r)} |{r}|");
					printIf(global.LOG_EXPRESSION, "====================");
					break;
			}
			
			return res;
		}
		
		static eval_real = function(v1, v2, _symbol = symbol) {
			switch(_symbol) {
				case "+": 
				case "⊕": 
					if(is_string(v1) || is_string(v2))	return string(v1) + string(v2);
					if(is_real(v1) && is_real(v2))		return v1 + v2;
					return 0;
				case "-": 
				case "⊖": return (is_real(v1) && is_real(v2))? v1 - v2		 : 0;
				case "∸": return is_real(v1)? -v1 : 0;
				case "*": 
				case "⊗": return (is_real(v1) && is_real(v2))? v1 * v2		 : 0;
				case "$": return (is_real(v1) && is_real(v2))? power(v1, v2) : 0;
				case "/": 
				case "⊘": return (is_real(v1) && is_real(v2) && v2 != 0)? v1 / v2 : 0;
				case "%": return (is_real(v1) && is_real(v2) && v2 != 0)? v1 % v2 : 0;
				
				case "&": return (is_real(v1) && is_real(v2))? v1 & v2       : 0;
				case "|": return (is_real(v1) && is_real(v2))? v1 | v2       : 0;
				case "^": return (is_real(v1) && is_real(v2))? v1 ^ v2       : 0;
				case "«": return (is_real(v1) && is_real(v2))? v1 << v2      : 0;
				case "»": return (is_real(v1) && is_real(v2))? v1 >> v2      : 0;
				case "~": return  is_real(v1)? ~v1 : 0;
				
				case "⩵": return (is_real(v1) && is_real(v2))? v1 == v2     : 0;
				case "≠": return (is_real(v1) && is_real(v2))? v1 != v2      : 0;
				case "≤": return (is_real(v1) && is_real(v2))? v1 <= v2      : 0;
				case "≥": return (is_real(v1) && is_real(v2))? v1 >= v2      : 0;
				case ">": return (is_real(v1) && is_real(v2))? v1 > v2       : 0;
				case "<": return (is_real(v1) && is_real(v2))? v1 < v2       : 0;
				
				case "sin"   : return is_real(v1)? sin(v1)    : 0;
				case "cos"   : return is_real(v1)? cos(v1)    : 0;
				case "tan"   : return is_real(v1)? tan(v1)    : 0;
				case "abs"	 : return is_real(v1)? abs(v1)    : 0;
				case "round" : return is_real(v1)? round(v1)  : 0;
				case "ceil"	 : return is_real(v1)? ceil(v1)   : 0;
				case "floor" : return is_real(v1)? floor(v1)  : 0;
			}
			
			return v1;
		}
	}
	
	function functionStrip(fx) {
		var el_st = 1;
		var el_ed = 1;
		
		for( var i = 1; i <= string_length(fx); i++ ) {
			var cch = string_char_at(fx, i);
			if(cch == "(") {
				el_st = i + 1;
				break;
			}
		}
		
		for( var i = string_length(fx); i >= 1; i-- ) {
			var cch = string_char_at(fx, i);
			if(cch == ")") {
				el_ed = i;
				break;
			}
		}
		
		return string_copy(fx, el_st, el_ed - el_st)
	}
	
	function evaluateFunctionList(fx) {
		fx = string_replace_all(fx, "{", "\n{\n");
		fx = string_replace_all(fx, "}", "\n}\n");
		
		var fxs = string_split(fx, "\n", true);
		
		var flist = new __funcList();
		
		var call_st = ds_stack_create();
		var blok_st = ds_stack_create();
		ds_stack_push(call_st, flist);
		
		for( var i = 0, n = array_length(fxs); i < n; i++ ) {
			var _fx = functionStringClean(fxs[i]);
			//print($"Eval line {i}: {_fx} [stack size = {ds_stack_size(call_st)}]");
			
			if(_fx == "" || _fx == "{") continue;
			if(_fx == "}") {
				ds_stack_pop(call_st);
				continue;
			}
			
			var _fx_sp = string_split(_fx, "(");
			var _cmd   = string_trim(_fx_sp[0]);
			var _cond  = functionStrip(_fx);
			
			switch(_cmd) {
				case "if":
					var con_if = new __funcIf();
					con_if.condition = evaluateFunctionTree(_cond);
					ds_stack_top(call_st).addFunction(con_if);
					ds_stack_push(call_st, con_if.if_true);
					ds_stack_push(blok_st, con_if);
					continue;
				case "elseif":
					var con_if = ds_stack_pop(blok_st);
					var con_elif = new __funcIf();
					con_elif.condition = evaluateFunctionTree(_cond);
					
					con_if.if_false.addFunction(con_elif);
					ds_stack_push(call_st, con_elif.if_true);
					ds_stack_push(blok_st, con_elif);
					continue;
				case "else":
					var con_if = ds_stack_pop(blok_st);
					
					ds_stack_push(call_st, con_if.if_false);
					continue;
				case "for":
					var con_for = new __funcFor();
					var cond    = string_splice(_cond, ":");
					if(array_length(cond) == 2) {
						con_for.itr_array = true;
						con_for.cond_arr  = evaluateFunctionTree(cond[1]);
						
						cond[0]  = string_trim(cond[0]);
						var _itr = string_split(cond[0], ",");
						if(array_length(_itr) == 1)
							con_for.cond_iter = cond[0];
						else if(array_length(_itr) == 2) {
							con_for.cond_indx = string_trim(_itr[0]);
							con_for.cond_iter = string_trim(_itr[1]);
						}
					} else if(array_length(cond) == 3) {
						con_for.itr_array = false;
						con_for.cond_init = evaluateFunctionTree(cond[0]);
						con_for.cond_iter = evaluateFunctionTree(cond[1]);
						con_for.cond_term = evaluateFunctionTree(cond[2]);
					}
					ds_stack_top(call_st).addFunction(con_for);
					ds_stack_push(call_st, con_for.action);
					continue;
			}
			
			if(ds_stack_empty(call_st)) {
				print("Block stack empty, how?");
			} else {
				var _top = ds_stack_top(call_st);
				_top.addFunction(evaluateFunctionTree(_fx));
			}
		}
		
		ds_stack_destroy(call_st);
		ds_stack_destroy(blok_st);
		
		return flist;
	}
	
	function evaluateFunctionTree(fx) {
		static __BRACKETS = [ "(", ")", "[", "]" ];
		
		var pres = global.EQUATION_PRES;
		var vl   = ds_stack_create();
		var op   = ds_stack_create();
		var last_push = "";
		
		var len = string_length(fx);
		var l   = 1;
		var ch  = "";
		var cch = "";
		var _ch = "";
		var in_str = false;
		
		printIf(global.LOG_EXPRESSION, $"===== Evaluating function: {fx} =====");
		
		while(l <= len) {
			ch = string_char_at(fx, l);
			
			//print($"Analyzing {ch}");
			
			if(ds_map_exists(pres, ch)) { //symbol is operator
				last_push = "op";
				
				if(ds_stack_empty(op)) ds_stack_push(op, ch);
				else {
					var _top = ds_stack_top(op);
					if(_top == "(" || ds_map_exists(global.FUNCTIONS, _top) || pres[? ch] > pres[? _top]) {
						ds_stack_push(op, ch);
					} else {
						if(ch == "-" && ds_map_exists(pres, _ch)) ch = "∸"; //unary negative
						
						while(pres[? ch] <= pres[? ds_stack_top(op)] && !ds_stack_empty(op))
							ds_stack_push(vl, buildFuncTree(ds_stack_pop(op), vl));
						ds_stack_push(op, ch);
					}
				}
				
				l++;
			} else if (ch == "(") {
				if(last_push == "fn")	ds_stack_push(op, [ "〚", ds_stack_size(vl) ]);
				else					ds_stack_push(op, ch);
				last_push = "op";
				l++;
			} else if (ch == ")") {
				while(!ds_stack_empty(op)) {
					var _top = ds_stack_pop(op);
					if(_top == "(") break;
					if(is_array(_top) && _top[0] == "〚") {
						var arr = [];
						while(ds_stack_size(vl) > _top[1])
							array_insert(arr, 0, ds_stack_pop(vl));
						
						ds_stack_push(vl, new __funcTree(ds_stack_pop(op), arr));
						break;
					}
					
					ds_stack_push(vl, buildFuncTree(_top, vl));
				}
				
				last_push = "vl";
				l++;
			} else if (ch == "[") {
				if(last_push == "vl") {
					ds_stack_push(op, "@");
					ds_stack_push(op, ch);
				} else
					ds_stack_push(op, [ "{", ds_stack_size(vl) ]);
				
				last_push = "op";
				l++;
			} else if (ch == "]") {
				while(!ds_stack_empty(op)) {
					var _top = ds_stack_pop(op);
					if(_top == "[") break;
					if(is_array(_top) && _top[0] == "{") {
						var arr = [];
						while(ds_stack_size(vl) > _top[1])
							array_insert(arr, 0, ds_stack_pop(vl));
						ds_stack_push(vl, new __funcTree("【", arr));
						break;
					}
					
					ds_stack_push(vl, buildFuncTree(_top, vl));
				}
				
				last_push = "vl";
				l++;
			} else if (ch == ",") {
				while(!ds_stack_empty(op)) {
					var _top = ds_stack_top(op);
					if(_top == "[" || _top == "(" || (is_array(_top) && _top[0] == "{")) break;
					
					ds_stack_push(vl, buildFuncTree(_top, vl));
				}
				
				last_push = "vl";
				l++;
			} else {
				var vsl = "";
				
				while(l <= len) {
					cch = string_char_at(fx, l);
					if(ds_map_exists(pres, cch) || array_exists(__BRACKETS, cch)) break;
					if(cch == ",") {
						l++;
						break;
					}
					
					vsl += cch;
					l++;
				}
				
				if(vsl == "") continue;
				
				if(ds_map_exists(global.FUNCTIONS, vsl)) { //function
					ds_stack_push(op, vsl);
					last_push = "fn";
				} else {
					vsl = string_trim(vsl);
					
					switch(vsl) {
						case "e" : ds_stack_push(vl, 2.71828);	break;
						case "pi": ds_stack_push(vl, pi);		break;
						default  : ds_stack_push(vl, isNumber(vsl)? toNumber(vsl) : vsl); break;
					}
					
					last_push = "vl";
				}
			}
			
			//print($"op: {ds_stack_size(op)}; vl: {ds_stack_size(vl)}");
			
			_ch = ch;
		}
		
		while(!ds_stack_empty(op)) 
			ds_stack_push(vl, buildFuncTree(ds_stack_pop(op), vl));
		
		var tree = ds_stack_empty(vl)? noone : ds_stack_pop(vl);
		
		ds_stack_destroy(op);
		ds_stack_destroy(vl);
		
		if(!is_struct(tree))
			tree = new __funcTree("", tree);
		
		printIf(global.LOG_EXPRESSION, tree);
		printIf(global.LOG_EXPRESSION, "");
		
		return tree;
	}
	
	function buildFuncTree(operator, vl) {
		if(ds_stack_empty(vl)) return noone;
		
		if(ds_map_exists(global.FUNCTIONS, operator)) {
			if(ds_stack_empty(vl)) 
				return noone;
				
			var _v1 = ds_stack_pop(vl);
			return new __funcTree(operator, _v1);
		}
		
		switch(operator) {
			case "-": //deal with preceeding negative number -5
				if(ds_stack_size(vl) >= 2) {
					var _v1 = ds_stack_pop(vl);
					var _v2 = ds_stack_pop(vl);
					return new __funcTree("-", _v2, _v1);	
				} else
					return new __funcTree("-", ds_stack_pop(vl), 0);	
				
			case "@": 
				var _v1 = ds_stack_pop(vl);
				var _v2 = ds_stack_pop(vl);
				return new __funcTree(operator, _v2, _v1);	
				
			case "+": //binary operators
			case "*": 
			case "$": 
			case "/": 
			case "%": 
			
			case "|": 
			case "&": 
			case "^": 
			case "»": 
			case "«": 
			
			case "=": 
			case "⩵": 
			case "≠": 
			case "≤": 
			case "≥": 
			case "<": 
			case ">": 
			
			case "⊕": 
			case "⊖": 
			case "⊗": 
			case "⊘": 
				
				if(ds_stack_size(vl) >= 2) {
					var _v1 = ds_stack_pop(vl);
					var _v2 = ds_stack_pop(vl);
					return new __funcTree(operator, _v2, _v1);	
				}
			
			default: return new __funcTree(operator, ds_stack_pop(vl));
		}
		
		return noone;
	}
	
	function evaluateFunction(fx, params = {}) {
		if(isNumber(fx)) return toNumber(fx);
		return evaluateFunctionList(fx).eval(params);
	}
#endregion