TERMINOLOGY.md

HAS Terminology: proc vs func

Decision: Keep Both Keywords

We use two distinct keywords for function-related constructs:

proc - Procedure Definition

• Purpose: Define a procedure/function with implementation
• Has body: Yes ({ ... })
• Generates code: Yes
• Example:

code main:
    proc add(a: long, b: long) -> long {
        return a + b;
    }

func - Forward Declaration

• Purpose: Declare a function without implementation (forward reference)
• Has body: No (semicolon terminated)
• Generates code: No
• Example:

code main:
    func helper(x: long) -> long;
    
    proc main() -> void {
        var result: long = helper(42);
    }
    
    proc helper(x: long) -> long {
        return x * 2;
    }

extern func - External Declaration

• Purpose: Declare external function from another module
• Has body: No
• Generates code: Only XREF directive
• Example:

code main:
    extern func vasm_function(x: long) -> long;
    
    proc main() -> void {
        var result: long = vasm_function(100);
    }

Comparison Table

Keyword	Implementation	Body	Assembly Output	Use Case
proc	Required	{ }	Full code	Define function
func	Later in file	;	None	Forward decl
extern func	External	;	XREF only	Import function

Rationale

This design follows C/C++ conventions:

• proc ≈ function definition
• func ≈ function prototype/forward declaration
• extern func ≈ external linkage declaration

The distinction makes code intent clear:

• proc: "I'm implementing this here"
• func: "I'll implement this later in this file"
• extern func: "This is implemented elsewhere"

Return Values

All functions return values in d0 register:

• byte functions: d0.b
• word functions: d0.w
• long functions: d0.l

Reading Return Values

// Method 1: Direct assignment (recommended)
var result: long = my_function(10, 20);

// Method 2: Use in expressions
var x: long = my_function(5, 3) + 100;

// Method 3: Pass to another function
var y: long = process(my_function(1, 2));

// Method 4: Call statement (return value in d0)
call my_function(10, 20);
var result: long = d0;

See examples/func_vs_proc.md for complete documentation.