Type Safety
The Cadence programming language is a type-safe language.
When assigning a new value to a variable, the value must be the same type as the variable.
For example, if a variable has type Bool,
it can only be assigned a value that has type Bool,
and not for example a value that has type Int.
// Declare a variable that has type `Bool`.
var a = true
// Invalid: cannot assign a value that has type `Int` to a variable which has type `Bool`.
//
a = 0
When passing arguments to a function,
the types of the values must match the function parameters' types.
For example, if a function expects an argument that has type Bool,
only a value that has type Bool can be provided,
and not for example a value which has type Int.
fun nand(_ a: Bool, _ b: Bool): Bool {
return !(a && b)
}
nand(false, false) // is `true`
// Invalid: The arguments of the function calls are integers and have type `Int`,
// but the function expects parameters booleans (type `Bool`).
//
nand(0, 0)
Types are not automatically converted.
For example, an integer is not automatically converted to a boolean,
nor is an Int32 automatically converted to an Int8,
nor is an optional integer Int?
automatically converted to a non-optional integer Int,
or vice-versa.
fun add(_ a: Int8, _ b: Int8): Int8 {
return a + b
}
// The arguments are not declared with a specific type, but they are inferred
// to be `Int8` since the parameter types of the function `add` are `Int8`.
add(1, 2) // is `3`
// Declare two constants which have type `Int32`.
//
let a: Int32 = 3_000_000_000
let b: Int32 = 3_000_000_000
// Invalid: cannot pass arguments which have type `Int32` to parameters which have type `Int8`.
//
add(a, b)