Operators

Operators are special functions defined in the Verse programming language to perform actions such as math operations on their operands. For example, in the expression 1 + 2, the + is an operator, and 1 and 2 are both operands.

There are three formats for operators that you’ll see in Verse:

• Prefix: There is only one operand and the operator is before the operand.
  

• Infix: There are two operands and the operator is between the operands.
  

• Postfix: There is only one operand and the operator is after the operand.
  

This page describes all the operators you can use in Verse, how they work, and their order of evaluation when used in combination with other operators.

List of All Operators and Operator Precedence

When multiple operators are used in the same expression, they are evaluated in the order of highest to lowest precedence. The table below lists all built-in operators in Verse and their precedence.

If there are operators with the same precedence in the same expression, then they are evaluated left to right. For example in the expression 3*2/4, both operators * and / have the same precedence, so 3*2 is evaluated first and its result becomes the left operand for the / operator.

You can change the order in which operators are evaluated by grouping expressions with (). For example, (1+2)*3 and 1+(2*3) don't evaluate to the same result. See Grouping for more details.

Comparison

You can control the success and failure flow with comparison expressions, which use the inequality and equality operators. Comparison expressions are failable, so you can only use comparison operators in failure contexts, such as in if expressions.

The table below describes each operator and what types it supports. All comparison operators use the infix format.

Both <>and = are also supported for array, map, tuple, and class instances, but with restrictions. The array, map, and tuple instances can only contain supported types, and class instances are only supported if they contain at least one var member.

Decision

You can control the success and failure flow with decision expressions, which use the operators not, and, and or. Decision expressions are failable, so you can only use comparison operators in failure contexts, such as in if expressions. You can use any expressions that succeed or fail with decision operators.

Not Operator

The decision operator not negates the success or failure of an expression. The not operator uses the prefix format.

For example, when expression fails, not expression will succeed. When expression succeeds, not expression will fail and the effects of expression are never committed (as if the expression never happened).

For example, after the following code is executed, Example will still have the initial value 0:

var Example : int = 0
if (not (set Example = ExampleArray[0])) { … }
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var Example : int = 0 if (not (set Example = ExampleArray[0])) { … }

You can use not not expression as a way to check if an expression will succeed but make it so the expression never happens.

Reference for the not operator evaluating an expression, represented by p.

And / Or Operators

The decision operator and uses the infix format and is a failable expression that succeeds if both operands succeed, or fails if at least one operand fails.

The decision operator or uses the infix format and is:

• A failure context for the first operand.
• A failable expression only if the second operand is failable.

The or operator skips evaluation of the second operand if the first operand succeeds.

The table below describes the results of all the operand combinations of success and failure for decision expressions using the operators and and or.

Reference for the and and or operators evaluating expressions, represented by p and q.

Math

With math expressions, you can do the four basic math operations (addition, subtraction, multiplication, and division) with number values, and add strings together. All the operators use the infix format, except + and - can also be a prefix for number values. There are also assign operators, e.g., set X += 10. They are almost the same as doing the operation and then assigning the result, set X = X + 10, the difference is that the X in this case is only evaluated once. The result of an assignment operator is the value used to update the variable.

The table below describes each operator and what types it supports.

Query

Query expressions use the operator ? (query) and check if a logic value is true. Otherwise, the expression fails. The ? (query) operator uses the postfix format.

Reference for the ? (query) operator evaluating expressions, represented by p.

For example:

if (IsMorning?):
    Say("Good Morning!")
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if (IsMorning?): Say("Good Morning!")