if
Use if to test a condition. If the condition cond is true, evaluate the then expression; otherwise, evaluate the else expression.
By convention, the data type <a> is used to represent type-bound parameters that serve as input for functions and expressions or for generic arguments.
Basic syntax
To test a condition and execute different expressions based on the result, use the following syntax:
(if cond then else)
Arguments
Use the following arguments to define the condition and expressions to be evaluated based on the outcome of the condition using the if Pact function.
| Argument | Type | Description |
|---|---|---|
cond | boolean | Specifies the condition to be tested. |
then | <a> | Specifies the expression to be evaluated if the condition is true. |
else | <a> | Specifies the expression to be evaluated if the condition is false. |
Return value
The if function returns the result of evaluating either the then expression or the else expression, depending on the outcome of the condition.
Examples
The following example demonstrates the use of if to test a condition in the Pact REPL:
pact>(if (= (+ 2 2) 4) "Sanity prevails" "Chaos reigns")
"Sanity prevails"
In this example, the condition (= (+ 2 2) 4) evaluates to true, so the expression "Sanity prevails" is returned.
pact>(if (= (+ 2 2) 5) "Sanity prevails" "Chaos reigns")
"Chaos reigns"
In this example, the condition (= (+ 2 2) 5) evaluates to false, so the expression "Chaos reigns" is returned.