typeof

typeof expr evaluates at compile time to a Str naming the type of the expression.

Syntax

typeof expr
typeof(expr)    // parentheses are optional

typeof always returns a Str. Since its result is a Str, typeof typeof x is valid and returns "Str".

Examples

print(typeof "abc")         // Str
print(typeof 2)             // Int
print(typeof true)          // Bool
print(typeof new Void)      // Void
print(typeof typeof Bool)   // Str

On classes and instances:

class C
print(typeof C)       // C
print(typeof new C)   // C

On functions and calls:

def a() {}
print(typeof a)      // Fn a() Void
print(typeof a())    // Void

Inside generic functions

typeof reflects the concrete type at the call site. Within the generic function body, typeof T prints the type parameter name as a string, not the concrete type:

def show<T>(a: T) T {
    print(typeof a, ",")     // prints "T"
    print(typeof T, ",")     // prints "T"
    return a
}
def main() {
    let int = show!<Int>(1)
    print(typeof int, ",")           // Int
    print(typeof show!<Str>("Hi"))   // Str
}
// prints T,T,Int,Str

Restrictions

The following are SyntaxError:

• typeof alone with nothing after it
• typeof 1 2 (two expressions)
• typeof () (empty parentheses)
• typeof while {} or typeof if true {} (control-flow as argument)

Using an undeclared name — typeof Foo where Foo is not defined — is an UnknownSymbol.