I've been trying to create a function in GDScript to process and calculate a string using PEMDAS rules. Below is my try on the subject. It can so far only use the MDAS rules:
Is there a better way to achieve such a function?
func _ready() -> void:
### USE CASES ###
print(Compute_String("1+2*3+3=")) # Output = 10
print(Compute_String("1+2*3*3=")) # Output = 19
print(Compute_String("1*2*3+3=")) # Output = 9
print(Compute_String("1+2+3*3=")) # Output = 12
print(Compute_String("5*2+7-3/2=")) # Output = 15.5
print(Compute_String("9+5.5*2.25=")) # Output = 21.375
print(Compute_String("5*2+7-3/2")) # Output = 1.#QNAN (Missing equals)
print(Compute_String("5*2+7-/2=")) # Output = 1.#QNAN (Adjacent operators)
print(Compute_String("*2+7-3/2=")) # Output = 1.#QNAN (Begins with operator)
print(Compute_String("")) # Output = 1.#QNAN (Empty)
print(Compute_String("=")) # Output = 1.#QNAN (Considered as empty)
print(Compute_String("1 +2=")) # Output = 1.#QNAN (Contains space)
print(Compute_String("(1+2)*3=")) # Output = 1.#QNAN (Parentheses not supported)
func Compute_String(_string: String) -> float:
var _result: float = NAN
var _elements: Array = []
if not _string.empty() and _string[_string.length() - 1] == "=":
var _current_element: String = ""
for _count in _string.length():
if _string[_count].is_valid_float() or _string[_count] == ".": _current_element += _string[_count]
else:
if _string[_count - 1].is_valid_float() and (_string[_count + 1].is_valid_float() if _string[_count] != "=" else true):
_elements.append_array([_current_element,_string[_count]]) ; _current_element = ""
else: return NAN
if not _elements.empty():
_elements.resize(_elements.size() - 1)
while _get_operators_count(_elements) != 0:
var _id: Array = [0, 0.0, 0.0]
if "*" in _elements:
_id = _add_adjacent(_elements, "*") ; _remove_adjacent(_elements, _id[0]) ; _elements.insert(_id[0] - 1, _id[1] * _id[2])
elif "/" in _elements:
_id = _add_adjacent(_elements, "/") ; _remove_adjacent(_elements, _id[0]) ; _elements.insert(_id[0] - 1, _id[1] / _id[2])
elif "+" in _elements:
_id = _add_adjacent(_elements, "+") ; _remove_adjacent(_elements, _id[0]) ; _elements.insert(_id[0] - 1, _id[1] + _id[2])
elif "-" in _elements:
_id = _add_adjacent(_elements, "-") ; _remove_adjacent(_elements, _id[0]) ; _elements.insert(_id[0] - 1, _id[1] - _id[2])
else: return NAN
if _elements.size() == 1: _result = _elements[0]
return _result
func _get_operators_count(_elements: Array) -> int:
var _result: int = 0 ; for _element in _elements: if not str(_element).is_valid_float(): _result += 1 ; return _result
func _add_adjacent(_elements: Array, _operator) -> Array:
return [_elements.find(_operator), float(_elements[_elements.find(_operator) - 1]), float(_elements[_elements.find(_operator) + 1])]
func _remove_adjacent(_elements: Array, _operator_idx: int) -> void:
_elements.remove(_operator_idx + 1) ; _elements.remove(_operator_idx) ; _elements.remove(_operator_idx - 1)
