Type Casting and Inference
Nim is a statically typed language. As such, each variable has a type associated with it. As seen in the previous example these types are inferred in the
var declarations by the compiler.
# These types are inferred. var x = 5 # int var y = "foo" # string # Assigning a value of a different type will result in a compile-time error. x = y
$ nim c -r typeinference.nim typeinference.nim(6, 4) Error: type mismatch: got (string) but expected 'int'
You may optionally specify the type after a colon (
:). In some cases the compiler will expect you to explicitly cast types, for which multiple ways are available:
- type conversion, whose safety checked by the compiler
- annotating the variable type
castkeyword, which is unsafe and should be used only where you know what you are doing, such as in interfacing with C
var x = int(1.0 / 3) # type conversion var y: seq[int] = @ # empty seq needs type specification var z = "Foobar" proc ffi(foo: ptr array[6, char]) = echo repr(foo) ffi(cast[ptr array[6, char]](addr z))
$ nim c -r typecasting.nim ref 002C8030 --> ['F', 'o', 'o', 'b', 'a', 'r']