---
title: Thesaurus rule syntax with numeric and Boolean parameters
slug: '1187'
canonical_url: https://docs.coveo.com/en/1187/
collection: coveo-for-salesforce
source_format: adoc
---
# Thesaurus rule syntax with numeric and Boolean parameters
Thesaurus rules could break some query extensions in specific scenarios.

When a thesaurus rule applies to a number or a Boolean and these values aren't between single quotes in the query extension, the values are expanded and cause an error.

**Example**

Thesaurus rule: expand 300, 30

Query extension: $qre(expression: foo bar, modifier: 300)

Result: $qre(expression: foo bar, modifier: 300 OR 30) -> **Query error**

> **Leading practice**
>
> **Always** surround numeric/Boolean parameters with single quotes.

**Example**

Thesaurus rule: expand 300, 30

Query extension: $qre(expression: foo bar, modifier: '300')

Result: $qre(expression: foo bar, modifier: '300') -> **Works**

> **Note**
>
> This happens because the Coveo Search API parses the different query arguments of an extension and manages the parameters differently depending on the type.
> 
> If the parameter isn't surrounded by single quotes, it will be considered as an expression that needs to be expanded.
> If the parameter is surrounded by single quotes, it will be considered as a literal and won't be expanded.
> The same principle applies to parameters that contain expressions.
> 
> If you want an expression to be expanded, which is typically the case, don't surround it with single quotes.