Control Structures

if

T core.if!(T)( cond:bool, ifTrue:block(T)(), ifFalse:block(T)() = noop )

An if statement takes a condition and executes the first block if it is true otherwise the other ( if provided ). The value of the executed block is returned.

	mutable cond = false;
	if (cond, sout.writeln("Not printed."));

	cond = true;
	if (cond, sout.writeln("Printed."));

	if (cond, sout.writeln("Printed."), sout.writeln("Not printed."));

	mutable cond = false;
	if (cond, sout.writeln("Not printed."), sout.writeln("Printed."));

Syntactic Sugar

It doesn't look that bad but when you get into if else's things start to get ugly. For ifs without an else clause you can use the trailing-block function call syntax. With an else clause the if statement has a special syntax using the else keyword.

	mutable cond = true;

	if (cond) sout.writeln("Printed");

	if (cond) sout.writeln("Printed");      // Now that's what you were looking
	else      sout.writeln("Not printed."); // for.

else if

By chaining if statements together you can easily achieve else if statements.

	mutable cond = 7;

	if      ( cond == 1 ) sout.writeln("1");
	else if ( cond == 2 ) sout.writeln("2");
	else if ( cond == 3 ) sout.writeln("3");
	else if ( cond == 4 ) sout.writeln("4");
	else if ( cond == 5 ) sout.writeln("5");
	else                  sout.writeln("I give up, it's big.");

while

() while!(T)( block(bool)() cond, block(uint)() code )

The while statement performs the following steps.

1. Evaluate cond. If true quit.
2. Evaluate code.
3. Go back to step 1.

	mutable tries:uint = 0;

	while ( 2^^tries < 1_000_000 )
		tries++;

	sout.write("You need ").write(tries, " bytes to store 1 000 000.");

dowhile

() dowhile!(T)( block(bool)() cond, block(uint)() code )

The same as while except it doesn't evaluate the condition on the first pass. (start at step 2)

for

() for!(T)( block()() init, block(bool)() cond, block()() inc, block(uint)() code )

The for loop performs the following steps.

1. Evaluate init.
2. Evaluate cond. If true quit.
3. Evaluate code.
4. Evaluate inc.
5. Go back to step 2.

The for loop cannot be expressed perfectly as a function call as the variables declared in the init block are available in the other three. If it were to be translated into a while loop it would look like.

	for ( {init} , {cond}, {inc} ) {code}

	// is equivalent to:

	{
		{init};
		while ({cond})
		{
			{code};
			{inc};
		}
	}