# When Construct in LISP

• Last Updated : 09 Nov, 2021

In this article, we will discuss the when construct. The when is a decision-making statement used to specify the decisions. It is similar to conditional statements.

Syntax:

`(when (condition) (statements) )`

where,

1. condition is a test statement used to test
2. statements are the actions that will depend on the condition

Example 1: LISP Program to check the number is equal to 50 or not

## Lisp

 `;set number to ``50` `(setq number ``50``) ` ` `  `;condition check the given number is ``equal` `to ``50`  `(``when` `(``=` `number ``50``) ` ` `  `;statement ` `  ``(``format` `t` `"Equal to 50"``) ` `   ``) `

Output:

`Equal to 50`

Example 2: LISP Program to check the given number with comparison operators

## Lisp

 `;set number to ``50` `(setq number ``50``) ` ` `  `;condition check the given number is ``equal` `to ``50`  `(``when` `(``=` `number ``50``) ` ` `  `;statement ` `  ``(``format` `t` `"Equal to 50"``) ` `   ``) ` `(terpri) ` `;set number to ``150` `(setq number ``150``) ` ` `  `;condition check the given number is greater than or ``equal` `to ``50`  `(``when` `(>``=` `number ``50``) ` ` `  `;statement ` `  ``(``format` `t` `"greater than or Equal to 50"``) ` `   ``) ` `(terpri)   ` `   ``;set number to ``10` `(setq number ``10``) ` ` `  `;condition check the given number is less than or ``equal` `to ``50`  `(``when` `(<``=` `number ``50``) ` ` `  `;statement ` `  ``(``format` `t` `"less than or Equal to 50"``) ` `   ``) `

Output:

```Equal to 50
greater than or Equal to 50
less than or Equal to 50```

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