Maths

Most games only need to add and subtract - a score, a health bar, a count of coins. This page covers that, and the rest of the maths Quest Viva can do when you need it.

Whole numbers and decimals

Quest Viva has two kinds of number: whole numbers (int), such as 3 or -250, and decimals (double), such as 2.5. Use whole numbers whenever you can:

• Dividing two whole numbers gives a whole number, dropping any remainder: 7 / 2 is 3. If either number is a decimal, the result is a decimal: 7 / 2.0 is 3.5.
• Decimals are approximate. 0.1 + 0.2 gives 0.30000000000000004, and Cos(pi / 2) gives 6.123233995736766E-17 rather than 0. That’s close enough for a calculation, but it doesn’t look right when printed.

For money, store the amount in pennies (or cents) as a whole number, and only format it when you print it. DisplayMoney does that using the format in game.moneyformat:

game.moneyformat = "£!1.2!"
msg ("That will be " + DisplayMoney(299) + ", please.")

That prints “That will be £2.99, please.” The same idea works for other quantities: to track a temperature to a tenth of a degree, store it in tenths, and print it with DisplayNumber (temperature, "1.1"), which shows 215 as 21.5. See DisplayMoney for the format.

Arithmetic

As well as +, -, * and /, you can use % for the remainder after dividing, and ^ to raise to a power:

msg ("13 mod 3 is " + (13 % 3))
msg ("2 to the 3 is " + (2^3))

That prints “13 mod 3 is 1” and “2 to the 3 is 8”. % is handy for telling whether one number divides exactly into another: n % 2 = 0 is true when n is even.

Rounding

There are four functions for rounding a decimal:

Value	Floor	Ceiling	Round	Truncate
3.14	3	4	3	3
3.6	3	4	4	3
-3.14	-4	-3	-3	-3
-3.6	-4	-3	-4	-3

Floor always rounds down, Ceiling always rounds up, Round goes to the nearest whole number, and Truncate just drops the decimal part. When a number is exactly halfway, Round goes to the nearest even number, so Round(2.5) is 2 and Round(3.5) is 4.

Round can also round to a number of decimal places:

msg ("The ship is " + Round(distance, 2) + " km away.")

With distance set to 12.345678, that prints “The ship is 12.35 km away.”

All four functions still give you a decimal, even though it has no fractional part - Round(4.56) is 5, but it’s the decimal 5. To turn it into a whole number, use cast, with no quotes around int:

whole = cast(Round(4.56), int)

Minimum and maximum

Min and Max give the smaller or larger of two numbers. They’re a neat way to keep a value within limits:

player.health = Min(player.health + 20, 100)

That adds 20 to the player’s health, but never takes it above 100.

Choosing a value with if

if can also be used as a function, which takes a condition and two values. It gives you the first value if the condition is true, and the second if it’s false:

msg ("The lamp is " + if (lamp.switchedon, "on", "off") + ".")

That does the same as this:

if (lamp.switchedon) {
  s = "on"
}
else {
  s = "off"
}
msg ("The lamp is " + s + ".")

Checking a list with in

in is true if the value on the left is in the list on the right:

colours = Split("red;green;blue", ";")
msg ("green" in colours)
msg ("pink" in colours)

That prints “True” and then “False”. You don’t need to make a list first - you can put the values in brackets:

if (game.pov.parent.name in ("kitchen", "larder", "scullery")) {
  msg ("You can smell baking.")
}

Indexing lists and dictionaries

You can get an item from a list or a dictionary with square brackets. Lists count from 0:

colours = Split("red;green;blue", ";")
msg (colours[1])

That prints “green”. colours[1] does the same as ListItem(colours, 1), and prices["apple"] does the same as DictionaryItem(prices, "apple").

Other functions

Quest Viva has these other maths functions, and the constants e and pi:

Function	Gives
Abs(-2)	The value without its sign: 2
Sign(-2)	-1 for a negative number, 1 for a positive one, 0 for zero
Sqrt(2)	The square root: 1.4142135623730951
Pow(2, 3)	2 to the power of 3: 8
Exp(7)	e to the power of 7
Log(7), Log10(7)	The natural logarithm, and the logarithm to base 10
Sin, Cos, Tan, Asin, Acos, Atan, Sinh, Cosh, Tanh	Trigonometry

The trigonometry functions work in radians, not degrees. To use degrees, multiply by pi / 180 first:

msg (Sin(30 * pi / 180))

That prints 0.49999999999999994 - which, as above, is how decimals go.

Don’t use e or pi as the names of local variables. Assigning to them is silently ignored, so they keep their values of 2.718… and 3.141….

Bitwise operations

and, or and xor also work on whole numbers, comparing them one binary digit at a time. << and >> shift the digits left or right:

msg (20 and 4)
msg (20 or 4)
msg (20 xor 4)
msg (3 << 3)
msg (24 >> 3)

These print 4, 20, 16, 24 and 3. Twenty is 10100 in binary and 4 is 100: and keeps the digits they both have (100, which is 4), or keeps the digits either has (10100, which is 20), and xor keeps the digits only one of them has (10000, which is 16). Shifting left by 3 multiplies by 8, and shifting right by 3 divides by 8.