[FUNC @ATOI [[PARAM !v $STRING] [RETURNS [INT]]] [
  [DEFINE !res 0]
  [DEFINE !sign 1]
  [DEFINE !i 0]
  [IF [= [GET !v 0] '-'] [
    [DEFINE !sign -1]
    [DEFINE !i 1]
  ] []]

  [WHILE [< !i [LEN !v]] [
    [DEFINE !res [+ [* !res 10] [TOI [- [GET !v !i] '0']]]]
    [DEFINE !i [+ !i 1]]
  ]]

  [RETURN [* !sign !res]]
]]

# My own naive implementation, will probably have rounding errors. Feel free to improve!
[FUNC @ATOF [[PARAM !v $STRING] [RETURNS [FLOAT]]] [
  [DEFINE !res 0.0]
  [DEFINE !sign 1.0]
  [DEFINE !i 0]
  [IF [= [GET !v 0] '-'] [
    [DEFINE !sign -1.0]
    [DEFINE !i 1]
  ] []]

  [DEFINE !dec [@FALSE]]
  [DEFINE !deccnt 0]
  [WHILE [< !i [LEN !v]] [
    [IF [= [GET !v !i] '.'] [
      [DEFINE !dec [@TRUE]]
    ] [
      [DEFINE !res [+ [* !res 10.0] [TOF [- [GET !v !i] '0']]]]
      [IF !dec [
        [DEFINE !deccnt [+ !deccnt 1]]
    ] []]
    ]]

    [DEFINE !i [+ !i 1]]
  ]]

  [RETURN [* !sign [/ !res [TOF [^ 10 !deccnt]]]]]
]]

[FUNC @ISINT [[PARAM !v $STRING] [RETURNS [BOOL]]] [
  [DEFINE !i 0]

  [IF [= [GET !v 0] '-'] [
    [DEFINE !i 1]
  ] []]

  [WHILE [< !i [LEN !v]] [
    [IF [| [> [GET !v !i] '9'] [< [GET !v !i] '0']] [
      [RETURN [@FALSE]]
    ] []]
    [DEFINE !i [+ !i 1]]
  ]]
  [RETURN [@TRUE]]
]]

[FUNC @ISFLOAT [[PARAM !v $STRING] [RETURNS [BOOL]]] [
  [DEFINE !i 0]

  [IF [= [GET !v 0] '-'] [
    [DEFINE !i 1]
  ] []]

  [DEFINE !hasdec [@TRUE]]

  [WHILE [< !i [LEN !v]] [
    [IF [= [GET !v !i] '.'] [
      [IF !hasdec [
        [RETURN [@FALSE]]
      ] [
        [DEFINE !hasdec [@FALSE]]
      ]]
    ] []]
    [IF [| [> [GET !v !i] '9'] [< [GET !v !i] '0']] [
      [RETURN [@FALSE]]
    ] []]
    [DEFINE !i [+ !i 1]]
  ]]
  [RETURN [@TRUE]]
]]