Clojure (pronounced like 'closure') is the programming language used to express rules in LoanPro’s Automation Engine (as well as trigger-based notifications and a few other areas of the software).

Most clients have  LoanPro help write their rules, but some basic familiarity with the language can also help you communicate those requests to our team.

Basic syntax

A Clojure formula hinges on operands, operators, and a whole bunch of parentheses.

• An operand is a number, value, or variable.
• An operator indicates an action performed on the operands.

For instance:

In the Clojure formula (+ 1 2) above, we have two operands, 1 and 2, and one operator, +, all enclosed in a set of parentheses. The operator always comes first, and tells you what you'll be doing to each of the operands that follow. When we're adding more than two operands, we still only need one operator.

With the longer examples, you might see how Clojure is more efficient than standard math notation. Small equations (+ 1 2) and (1 + 2) look about the same, but the difference is more noticeable on larger equations.

Taking a closer look at that example, you'll notice how Clojure deals with multilayered equations. With a standard math equation, we might write (15 + 22) * (35 - 65), where parentheses show us that we should solve the two smaller questions before multiplying them together. Clojure similarly uses parentheses to show the order each operation should be performed in. This equation would be written (* (+ 15 22) (- 35 65)). Clojure works from the inside out: We first solve the two inner problems, then multiply them together.

With an understanding of basic Clojure syntax, you’re ready to learn how Clojure works in LMS. Clojure formulas become useful for automations when you add two other considerations:

• Operands don't have to be a static number. If you put a variable in a rule, the system will pull values from a specific loan or customer when it evaluates their account.
• Operators aren't limited to basic math. There's also comparison, logic, and utility functions.

Variables

Let's use the example (+ 1 x). In this rule, x is a variable, a placeholder for another value. As you plug in different values for X, the formula will give different answers. In LMS, there are dozens of values related to loans and customers, and we can use a variable to pull these values from the system. For example, let's write a Clojure formula that will give us the sum of the next payment and the amount that's already past due.

(+ status-next-payment-amount status-amount-due)

These variables are long and descriptive enough that you can tell at a glance what each means, but from a math perspective, this formula is as simple as (+ x y). When this formula runs on a loan, the system will pull the actual numbers and solve the equation, giving us a dollar amount as our answer.

While those two variables pull numbers (in this case, a dollar amount), others will pull dates or even text. The variable loan-status, for example, will return something like "Open - Repaying", depending on how your loan statuses are configured.

We maintain an article with a full list of available variables.

Other operators

So far, we've only seen examples with basic math functions as the operators. But there are also operators that perform different kinds of functions. Some return a number, like our math functions, but others will return a true-or-false value. These operators are used for the Automation Engine:  When a rule evaluates to true, the system will apply an effect on the loan.

Comparisons

Comparisons refer to basic valuations of whether one value is bigger, smaller, or equal to the next. The basic comparisons include greater than >, less than <, greater than or equal to >=, and less than or equal to <=. There's also equality = and inequality not=. All of these operators can work on multiple operands, and each will will return a true-or-false answer.

Logic

Logical operators can make judgements about their operands, which are always formulas. They include and, or, and not. The and operator evaluates to true if all of it's operands are true formulas. The or operator, on the other hand, will evaluate as true if at least one of the operands is true. Compare these two formulas:

The not operator works a little differently, only evaluating a single operand. A not formula will be true if the operand is false.

A practical use for not formulas is writing a rule that excludes a specific loan status or portfolio:

(not (= loan-status "Closed - Paid Off"))

In that formula, loans with that status will evaluate as false, and the affect won't apply to them.

Utility functions

Utility functions perform special operations. They always start with v/ and will return different types of answers depending on the function.

Text to a whole number

You can extract a whole number from a string of text using the “v/parse-int” operator. Text is often enclosed in double quotes, and dates are automatically converted to text when needed.

Text to a floating point number

The LoanPro Computation Rules also allow you to extract floating point numbers from a string of text using the “v/parse-float” operator. The examples used in the section above apply the same here but for floating point numbers, instead of whole numbers.

Substring

The Substring operator (subs) evaluates a text operand and returns a smaller portion of it. The substring operator takes two to three operands: The text to use as a base, the starting character (the first character is 0, the second is 1, and so forth), and the ending character (if not provided then it will include everything to the right of the starting character).

Note that the ending character is exclusive; in other words, the result will not include the end character.

Maximum and minimum

The maximum (max) operator returns the highest operand given, and the minimum (min) operator returns the lowest. They can take any number of operands.

Positive and negative

The positive (pos?) and negative (neg?) operators look at a number and return either "True" or "False".

Dates

There's countless situations where you need to measure or calculate time on loans, but you can’t just add March 3rd to June 9th like a normal math equation. LoanPro has variables for dates and special functions that let you compare them. 

LoanPro has two options for getting today’s date. The first is a special command:

(v/today :format :date)

This function, v/today, will get the current date from the system at the time the rule is evaluated. This date will be in UTC time, and is pulled from the LoanPro servers. 

The other option is to use the current-date variable, which outputs the tenant time zone’s current date as a string.

Comparing dates

LoanPro uses the operator “v/date-compare” to find the number of days between two dates, subtracting the first date from the second date. If the second date is larger than the first date you will get a negative number; otherwise you will get a positive number.

So, let’s say you want to know how many days it’s been since the last payment date for a loan. You would enter the following:

(v/date-compare current-date last-payment-date)

If you want to know how many days until the next due date you would enter the following:

(v/date-compare current-date status-next-payment-date)

This would give me a positive number representing the number of days until the next due date for a loan, expressed as a negative number. If you flip the order of the dates, then you flip the sign of the result.

When you want to compute a specific date, make sure your output format is set to 'Date'. When you want to get how much time is between two dates, make sure your output format is set to 'Number'.

You can also use the operator "v/banking-days-between", which, as the name suggests, counts the number of banking days between two dates:

 (v/banking-days-between current-date last-payment-date)

Adding and subtracting days from a date

Sometimes we want to know the date so many days before or after a different date. For example, maybe we want to know which date is five days past the next due date so we can send a late payment notice if the customer doesn’t pay on time. This is accomplished with two different operators, “v/date-+” to add days to a date and “v/date−−” to subtract days from a date. These operators require the first operand to be a date and the second operand to be a number. The following code examples would work:

✔ (v/date-+ current-date 5)

✔ (v/date-+ current-date (v/date-compare status-next-payment-date loan-create-time))

The following are examples of codes that don’t work:

✘ (v/date-+ 5 current-date)

✘ (v/date-+ current-date loan-create-time)

Dates before or after a specific day of the month

LoanPro provides two functions that let you evaluate whether a date is before or after a specific day of the month. These functions are:

(v/before-nth-of-month)

(v/after-nth-of-month)

Non-variable dates

Sometimes we want to compare dates to a specific point of time that won’t change based on loan settings. For example, we may want to know how many days have passed since February 23rd, 1994. To use a static or non-changing date, we must put it in quotation marks and have the year, then the month, and then the day. Once we do this, we can use it like any other date. For example, to use February 23rd, 1994 as a date, we would type:

“1994-02-23”

Rules Manager

Even once you've got the hang of Clojure, it can be time consuming to write out the same rule in several different places. The Rules Manager solves this problem—you can save a list of rules, and then pull from that list any time you're writing one.

In LMS, the rules manager is located in Settings > Company > Rules Manager.

You'll see a list of the existing rules saved in your system. These will be available anytime you're asked to write a rule. Each entry includes the name, the text of the rule itself, whether and how the answer is rounded, and the type of output it yields. To create a new rule, the blue 'Add' button in the top right corner. That'll bring up this window with fields for basic info, and one large field where you can enter your Clojure rule.