For arithmetic in Velocity, the only safe approach is the so-called “tools-ish” one: use MathTool methods like \$math.add, \$math.sub, and  \$math.mul.

### The rule

Aside from the one exception later in this post, you should not use the Java-like math operators (+ and -).

The core reason is the plus sign + and minus sign - have different syntax rules in Velocity! You can easily create fatal errors – or worse, lines that are silently ignored – by forgetting that - must be surrounded by spaces.

That’s right, only one of these is correct Velocity syntax for subtraction:

``#set( \$a = 99 )#set( \$b = \$a - 1 ) ## correct#set( \$b = \$a -1 ) ## fatal ParserException!#set( \$b = \$a- 1 ) ## fatal ParserException!#set( \$b = \$a-1 ) ## non-fatal, but doesn’t subtract!!!‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

So I always teach people to use #set( \$b = \$math.sub(\$a,1) ). It’s longer, but you’ll never break your code by switching sub and add.

### The exception

Despite the above, in the course of developing my Base64 encoding in Velocity code, I discovered a unique requirement that could only be met by purposely using the + operator instead of \$math.add.

This is the only exception I’ve found, and it doesn’t override my recommendation above. But it is – to me and I hope to the couple of people like me out there – fascinating.

So.

In Base64 encoding, one of the steps requires Integers to be converted to binary Strings, 42 → “00101010”. (If this is complete gibberish to you, you can reread this post when you have a couple more years of development under your belt!)

To get those Integers, you need to convert signed Bytes (-128 through 127) to their equivalent all-positive Integers (0 through 255).

To convert signed Bytes, you need to use a bitwise AND. But the traditional AND operator, the & symbol in Java and most other languages, isn’t available in Velocity.

Since you can’t use notation like #set( \$c = \$a & \$b ) in Velocity (that’s a fatal parser error) you need to find a method-based way – a “tools-ish” way, somewhat ironically – to do a bitwise AND: something like #set( \$c = \$a.and(\$b) ).

Miraculously, such a method does exist (after you do some hunting) so long as \$a is a Java BigInteger.

Hmm. So now you need to be able to construct a BigInteger from an Integer.

#### Getting a BigInteger

A BigInteger isn’t something you can explicitly create in Marketo’s Velocity (post-June 2019, that is), only implicitly. There’s one way to cheat it, and that is to set a variable to just outside of the range of a Long. If you know off the type of your head that the max positive Long is 9,223,372,036,854,775,807 (~9 quintillion) then you can add 1 to that:

``#set( \$aBigInteger = 9223372036854775808 )\${aBigInteger.class} ## will be class java.math.BigInteger‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

#### Skipping the magic

But let’s say you don’t know that magic number – you only know that Java’s

concrete integer Number types  are, in order of increasing width, Byte → Short → Integer → Long → BigInteger. (I think it’s reasonable for a developer to know that progression, but not reasonable to expect someone to remember that 9,223,372,036,854,775,807 is special.)

If you didn’t know the magic Long-BigInteger boundary, how would you make sure Velocity allocated a type big enough for a BigInteger? You’d want to say:

Gimme a Number that can hold Long.MAX_VALUE + 1.

Of course to do that, you‘d have to get a handle on a Long (in order to refer to the constant Long.MAX_VALUE). Since Velocity doesn’t give you a Long unless you’ve asked for something bigger than an Integer, you have to say:

First, gimme a Number with the value 0. I know that’s an Integer, since that’s the default type for whole numbers in Velocity.

Then, gimme another Number that can hold ThisMustBeAnInteger.MAX_VALUE + 1. That’s gonna be a Long.

Finally, gimme yet another Number that fits ThisMustBeALong.MAX_VALUE + 1. That third number must be a BigInteger.

And here is where + acts differently from \$math.add.

#### MathUtils vs. MathTools

Hidden in the doc for Velocity’s MathUtils (part of Velocity’s internal API, not for public consumption) you’ll find this gem: So now we know Velocity can do – in fact is explicitly documented to do – exactly what we need. If we add 1 to the max value of a Long, the result will be a BigInteger (and will also have the correct value, obviously).

Except this only applies to the literal + operator. MathTools’ \$math.add also does addition, but doesn’t implement the “overflow correction” logic.

Let’s compare.

Using the + operator:

``#set( \$Integer = 0 )Integer \$Integer.class.getName() = \$Integer#set( \$Long = \$field.in(\$Integer).MAX_VALUE + 1 )Long \$Long.class.getName() = \$Long#set( \$BigInteger = \$field.in(\$Long).MAX_VALUE + 1 )BigInteger \$BigInteger.class.getName() = \$BigInteger‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

The output will be:

``Integer java.lang.Integer = 0Long java.lang.Long = 2147483648BigInteger java.math.BigInteger = 9223372036854775808‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

Exactly what we need. \$BigInteger is a BigInteger we can use as a factory to make more BigIntegers (\$BigInteger.valueOf) and then do fancy stuff like .and() and .or() and  .xor() which would otherwise be impossible in Velocity.

``#set( \$Integer = 0 )Integer \$Integer.class.getName() = \$Integer#set( \$Long = \$math.add(\$field.in(\$Integer).MAX_VALUE,1) )Long \$Long.class.getName() = \$Long#set( \$BigInteger = \$math.add(\$field.in(\$Long).MAX_VALUE,1) )BigInteger \$BigInteger.class.getName() = \$BigInteger‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

The output will be:

``Integer java.lang.Integer = 0Long java.lang.Long = 2147483648BigInteger java.lang.Long = 9223372036854775807‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍``

Whoa. We attempted to add 1 to the largest Long, but the attempt silently failed. \$BigInteger (despite the name) remains a Long, and it never gets incremented: it’s still Long.MAX_VALUE or 9,223,372,036,854,775,807.

### It’s notable, but doesn’t change the rule

The likelihood that you’d otherwise need to perform BigInteger-range arithmetic within Marketo is basically zero.

I mean, it would have to be something like… you’re using a webhook to take the squares of lead scores, and you have a score in the millions and must raise it to the power of 2 in a Velocity token. Let’s face it, relative to the chances you will at some point forget the spaces around -, that’s just not gonna happen.  The risk/reward overwhelmingly favors \$math.add and \$math.sub.

In this case we needed a BigInteger not because of its infinite range of values, but because we need to get at the cool methods it has – which Integers and Longs do not. (The underlying value is tiny, between -128 and 127 then converted to between 0 and 255.) So for this particular purpose, deliberately using + makes sense.