Use of Functions

• Functions
  • Declarations
  • Implementation
  • Parameters
  • Return Values
  • Parameter And Return Value Types
  • Calls
  • Explanation Of Multiple Return Values

Functions

• Function Declarations

  function aFunction();

  If a function is not declared, it will be declared at the location where it is implemented.

• Function Implementation

  function aFunction() {
      // Codes
  }

• Function Parameters

  A function can have one or more parameters, separated by commas. Parameter passing and return value passing are done through runtime value type variables (EUDVariable).

  function printTwoVariableValues(parameter1, parameter2) {
      println("{}, {}", parameter1, parameter2);
  }

• Function Return Values

  A function can return one or more values after being called, with multiple return values separated by commas.

  function exchange(value1, value2) {
      return value2, value1;
  }

• Parameter And Return Value Types

  Function parameters and return values can set types.
  To set the parameter type, add a colon after the parameter name and write the type name, indicating that the runtime parameter value (as a number or pointer) will be set to the specified type.
  To set the return value type, add a colon after the closing parenthesis of the function declaration parameter list and write the type name, indicating that the returned runtime value (as a number or pointer) will be set to the specified type.

  function createANewUnit(player : TrgPlayer, ut : TrgUnit, loc : TrgLocation) : CUnit, TrgString {
      const cu = CUnit.from_read(EPD(0x628438));
      if (cu == 0) {
          return 0, $T("Unable to create unit");  
      }
      CreateUnit(1, ut, loc, player);
      if ( Memory(0x628438, Exactly, cu.ptr) ) {  
          return 0, $T("CreateUnit failed to create the unit, possibly incorrect parameters or the location can no longer place more units.");
      }
      return cu, $T("Success");
  }
  
  function onPluginStart() {
      const cu, err = createANewUnit(P1, $U("Terran Marine"), $L("Location 1"));
      if (cu != 0) {
          cu.cgive(P8);
          cu.set_color(P8);
      } else {
          DisplayTextAll(err);
      }
  }

• Function Calls

  aFunction(); // Directly call a function without arguments
  
  var a = 2;  
  var b = 3;
  
  a, b = exchange(a, b); // Pass arguments to call a function and get its return value
  
  printTwoVariableValues(a, b); // Pass arguments to call a function   

• Explanation Of Multiple Return Values

  A function that returns multiple return values actually returns a compile-time tuple. When you do not need to get all the return values, you can use selection [[]] to get one or more (starting from index 0) from the returned tuple.
  A tuple is a compile-time type, not a runtime data structure.

  function aFunctionWithMultipleReturnValues() {
      return 1, 2, 3, 4, 5;  
  }
  
  const r1 = aFunctionWithMultipleReturnValues()[[0]];
  
  const r4, r3 = aFunctionWithMultipleReturnValues()[[4, 3]];
  
  const r1, r2, r3, r4, r5 = aFunctionWithMultipleReturnValues(); // When there are enough left values to receive multiple return values, the tuple will automatically unpack