Types

Type declaration

A type determines a set of values that have the same operations and functions specific for those values. A type is denoted by a type name. A map is a group of elements of one type, indexed by a set of unique string keys. By default, arr and map arrays consist of strings, but you can specify any nested types by separating them with a dot. Note that variables of types arr, map, buf, set, obj and types that has been defined with struct, unlike other types, are passed by reference, not by value. This means that if you change the value of this parameter inside the function, you will change the original variable.

TypeName  = identifier { "." identifier }

The Gentee language predeclares the following types.

arr bool buf char error finfo float handle int map obj range set str time trace thread

Name	Description	Values	Initial value
int	64-bit integer type	-9223372036854775808 .. 9223372036854775807	0
float	64-bit double	2.22 E–308 .. 1.79 E+308	0.0
bool	boolean type	true or false	false
str	string	a sequence of bytes	empty string
char	Unicode character	Unicode code point int32	space
arr	array	array of elements	empty array of strings
map	associative array	associative array of elements	empty associative array of strings
buf	array of bytes	array of uint8	empty array
set	set of bool	array of uint64 with 1 bit per value	empty set
obj	object	int, bool, float, str, arr.obj, map.obj	nil
handle	hidden type	any Golang type	nil

The handle type is used to pass values between built-in Golang functions. A variable of this type can contain a value of any Golang type. Go functions should keep track of the types of received values, which are described as handle in Gentee.

arr.map.int a
map.arr.str b   // the same as map.arr b
map.bool c
arr.int  d

Type casting

There is no automatic type casting in Gentee . For basic types, there are functions for converting from one type to another, their names are the same as the name of the resulting type.

	int	bool	str	char	float
int		int(false)	int("-23")	int('A')	int(3.24)
bool	bool(1)		bool("0")		bool(1.1)
str	str(20)	str(false)		str('z')	str(5.662)
char
float	float(10)		float("-2E-34")

int(false) // = 0           
int(true) // = 1    
bool(0) // = false  
bool(0.) // = false  
bool(integer except zero) // = true    
bool("")  bool("0") bool("false") //=false
bool("not empty, zero or false string")   //=true

Type definition

You can define a structure type by using the struct keyword. Specify a type name after the keyword, and list the field types and names inside the curly braces. All fields in a variable of a structured type are automatically initialized. All variables of these types are passed by reference, rather than by value, when passed to functions. To assign or get a field value, specify its name after the dot.

structDecl = "struct" identifier "{" FieldDecl { newline  FieldDecl } "}"
FieldDecl = TypeName identifier
FieldExpr = PrimaryExpr "." identifier

struct my : int ID; str name
struct myStruct {
      int ID
      my myval
      arr st_arr
      map.int st_map
}
run int {
    myStruct ms
    ms.ID = 20
    return ms.ID * 2
}

Function type

The Gentee language allows you to work with function identifiers. You can get the ID of the function, pass it as a parameter and call the corresponding function. To work with function identifiers, you must define a function type using the fn keyword and specify the types of parameters and return value. To get the function ID, specify &function_name.fn_type. The function identifier can be passed in parameters or assigned to a variable of the corresponding fn type. To call a function by its identifier, it is sufficient to specify the variable name and parentheses with parameters, as when calling a function by name.

The function identifier does not apply to the following functions:

• Built-in functions.

• Functions with a variable number of parameters.

• Functions with optional variables.

fnDecl = "fn" FnName [FnParameters] [ TypeName ]
FnName = identifier
FnParameters     = "(" [ FnParameterList ] ")"
FnParameterList  = TypeName { [","] TypeName }
FnIdent = "&" FuncName "." FnName

fn bin( int int ) int
func add( int i, int j ) int : return i + j
func sub( int i, int j ) int : return i - j
func mybin(int i j, bin f ) int : return j + f(i, j)

run int {
  bin isub = &sub.bin
  return mybin(1, 2, &add.bin) + mybin(3, 7, isub)
}