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Declaring functions ​

Functions are declared with the fn keyword. Like types and values, they may be declared public with pub.

The main function is the program entry point. It shall return void or a signed integer type, and it shall not declare parameters. Command-line arguments are obtained through the allocator-aware @argsalloc[A](ac) intrinsic.

The following main function prints its command-line arguments. @argsalloc returns a result[list[ref u8], E] containing the arguments as raw strings; the list is released with @listfree.

spectre
val allocators = use("std/allocators")
val stdio = use("std/stdio")

pub fn main() void = {
    val ac: allocators.HeapAllocator = @zeroed
    val arguments: list[ref u8] = @argsalloc[allocators.HeapAllocator](ac)?
    defer {
        @listfree(arguments)
    }
    for arg in arguments {
        stdio.puts(arg)
    }
}

The reference implementation also retains the non-allocator @args() form for compatibility, but new code should use @argsalloc.

Inline functions ​

The inline modifier asks the compiler to expand a function at its call sites. It may be combined with trust when the body also needs a trusted context:

spectre
fn mix(a: i64, b: i64, c: i64) i64 = inline {
    return (a * 31 + b * 17 - c * 13) ^ ((a + b) << 3)
}

fn peek(ptr: ref u8) u8 = inline trust {
    return @load8(ptr) as u8
}

The modifier is a performance hint; it never changes the observable behaviour of the program. Both the QBE backend and the C backend accept it, and calls to simple inline functions are expanded even in the QBE path.

Extern functions ​

External functions are declared with the extern fn construct:

spectre
pub extern (C) fn my_malloc(size: usize) ref void = "malloc"

The example uses the libc malloc function. Depending on the linked libraries, any raw C symbol may be used in place of malloc.

Other considerations ​

The language has no closures and no nested function declarations. This restriction keeps control flow explicit and reduces complexity in the compiler.