template mytempl(prefix) =
proc $prefix & World() = echo "hello world"So that:
mytempl(hello)creates a function named "helloWorld"
You do it like this:
template mytempl(prefix) =
proc `prefix World`() = echo "hello world"
See here:
https://nim-lang.github.io/Nim/manual.html#templates-identifier-construction
Oh yes, I could have made that more clear.
Indeed, the default type is untyped. Both for the arguments as well as the return type.
And yes, untyped is required to make this work. Essentially untyped is just considered as a raw Nim identifier (nnkIdent in macro terms). If you used string as an argument, the compiler would understand that as a string at runtime. Since the name of the generated proc / etc. has to be known at compile time of course, this wouldn't work.
You can (although I don't think with a template) hand a static string, which is a string known at compile time and extract an identifier from the string. But unless you do more complicated macro things where you might want to calculate names of procs you want to generate, this won't be much different than just handing a raw identifier.
An example:
import macros
macro genproc(prefix: static string): untyped =
let procName = ident(prefix & "World")
result = quote do:
proc `procName`() = echo "Hello world"
genProc("hello") # works, string literal is static
helloWorld()
const foo = "alsoHello"
genProc(foo) # a const string is known at CT
alsoHelloWorld()
# and also
proc getName(): string =
result = "finalHello"
var bar {.compileTime.}: string
static: bar = getName() # some CT computation
genProc(bar)
finalHelloWorld()