Math and comparing values

Anywhere the editor asks for a number, you can give it a small calculation instead. That lets a value depend on other values: a score that is kills times ten, a price that goes up with your reputation, a cost that halves once you have a discount.

Where you can calculate#

A number can be a calculation in all of these places:

• Set to, Add and Subtract on a choice or an arrival.
• Both ends of Roll a number from … to …, and the percent in Set to yes some % of the time.
• The position in Get the item at a position in a list.
• The number you add to a list of numbers.

The simple row#

By default a number is a small row of three parts: a first operand, an operation, and a second operand.

• Each operand is either a fixed number you type or one of your number values. Pick a number from the dropdown to type one.
• The operation menu offers +, −, × and ÷. Leave it on "(just that)" and the row is only the first operand.

Advanced formulas#

For anything longer, turn on advanced mode. Either click the small "advanced" link beside a calculation, or tick Advanced expressions in the three-dot menu next to Submit. The setting is remembered in your browser for every story, and a calculation that is too long for the simple row switches to advanced by itself.

Advanced mode is a single text box where you type the formula using your values' names and the symbols + − * / and brackets.

value… beside the box inserts a value's exact name, so you never have to guess a spelling. If the formula cannot be understood, a message appears under the box. For a formula with brackets or several steps, the editor also spells out how it reads it. A "simple" link switches back when the formula is short enough.

A few formulas:

• kills * 10 for a score.
• (strength + luck) / 2 for an average.
• coins - price to work out change.

Names use letters, numbers and underscores, with no spaces. That is why the editor asks for them when you create a value.

Rules of the road#

• Effects on a choice run from top to bottom, and each one sees the results of the ones above it. Set a value first, then use it in the next effect.
• Dividing by zero gives 0 and does not break anything.
• Fractions are kept exactly while the story runs. Where a number is printed in the text, it is rounded to two decimal places.
• A calculation only uses number values and numbers you type. It cannot look at text or lists.

Comparing one value to another#

A check on a number normally compares against a number you type. You can also compare against another number value. In the check, open the dropdown where the number goes and pick a value instead of a number. Text checks can compare against another text value the same way.

That is enough for "the reader's strength is at least the guard's strength".

There is no arithmetic inside a check. If you need "strength plus luck is at least 10", calculate it first. Use ＋ Set a value on arrival to set a helper value called power to strength + luck, then check power.

What it cannot do#

There are no functions such as rounding, minimum or maximum. Do these with a fork instead. To keep a value from going above 10, add a fork after the change that says "if coins is more than 10, set coins to 10", and otherwise carry on.

Next#

Calculations are predictable. To bring chance in, read Randomness.