Operators and expressions

A coin adds one to a count, multiplies that count by a score value, and checks whether a goal condition has been met. Operators turn those small values into a decision.

The problem

ScoreCounter.AddCoins uses += twice. The second assignment combines multiplication and addition while preserving the order C# evaluates them.

When to reach for it

Use arithmetic for numbers, comparisons for decisions, and logical operators to combine booleans. The conditional ?: chooses one of two values. Null-coalescing ?? supplies a fallback. Null-conditional access ?. or ?[ guards the receiving pin and skips the access when the receiver is null.

Round Trip models a compound assignment as a SET fed by an operation. Score += amount is a Score read flowing through Add and back into the Score SET. The source spelling remains += while that operation still reads the same value it sets.

An operation produces a value and never runs on its own, so the menu that opens when you drop a wire from an execution pin onto empty canvas leaves out the arithmetic, Concat, comparison, and logical rows. Place them from empty canvas or from a data pin, then wire their result into the statement that uses it.

See it

Figure 1. Coins += count and the score calculation as a read feeding an operation that feeds a SET.

Do it

1. Right-click empty canvas and open the operators category.
2. Pick an arithmetic operation such as Add, Subtract, Multiply, Divide, or Modulo. Integer inputs also offer bitwise and shift operations.
3. To join text, pick Concat. Its result is a string from the start, and either side can take a string or another value, as in "score: " + points.
4. Fill the left and right pins with wires or literals. The result pin takes its type from the operands.
5. For a boolean result, choose a comparison such as Equals, Greater Than, or Less Than, or combine booleans with And and Or.
6. Use a conditional value when one condition selects between two results. Use a coalescing value when a missing left value should fall back to the right.
7. To alter an existing operation, right-click it and choose change operator. The offered choices are filtered by the operand types. Concat, comparison and logical operations have no change operator row.
8. Connect an operation back into the SET for the same target when you want read-modify-write behavior.
9. Press Compile. Round Trip recomposes the containing statement with C# precedence and required parentheses.

You should see

The graph shows each input and result separately. Source keeps an existing compound spelling when it still means the same thing, and receives longhand assignment for a new operation built on the canvas.

Change one thing

In AddCoins, use change operator on the score’s Add operation, preview the draft, then undo before Compile. Watch the source remain untouched while the graph changes.

What it writes

C#

What it writes

C#

Coins += count;
Score += count * _rules.coinScoreValue;
var label = title ?? "score";
var value = isBonus ? bonusScore : regularScore;
_audio?.PlayCoin();

When it goes wrong

When it goes wrong

Symptom	Check	Fix
An operator choice is missing	Check the operand types.	Connect compatible values first, then open change operator again.
Compile reports a missing operand	Look for a hollow left or right pin.	Wire or type every required operand.
A compound assignment becomes longhand	See whether the operation still reads the same target the SET writes.	Restore that read if the compound meaning is intended.

Next

• Arrays, tuples, and ranges
• Branch
• Preview and Compile