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Overview

Variables in PromptL allow you to store and reuse dynamic values across your prompt. They make your prompts more maintainable and adaptable by eliminating repetitive text and enabling dynamic content generation. Variables are defined using double curly braces ({{ }}) and can be used directly in text or as part of logic expressions.

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Defining Variables

You can define a variable by assigning a value inside {{ }}:
In this example:
  • The variable name is assigned the value "Alice".
  • The variable is interpolated into the text when the prompt is processed.

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Interpolating Variables

Variables can be used anywhere in your prompt. When interpolated, their value replaces the placeholder in the text.

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Input Parameters

Variables don’t have to be defined in the prompt. Instead, their values can be provided as dynamic input parameters when the prompt is executed.
In this example, the name variable can be defined in the code when running this prompt, allowing you to dynamically customize the output without modifying the prompt.

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Built-in Variables

PromptL provides special built-in variables that are automatically available in your prompts without needing to be defined.

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Current Date and Time

The $now variable returns the current date and time in ISO format:
This will output something like: Today is 2024-01-15T10:30:45.123Z. You can also use $now in expressions:
$now is an instance of Javascript Date class, and you can call any of its methods and properties.

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Default Values

You can define default values for variables using the || operator. If the variable is not defined in the prompt or provided as an input parameter, the default value will be used.
Here, the name variable will default to "Alice" if no value is provided.
Tip: Use default values to ensure your prompts remain functional even if some parameters are missing.

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Expressions

PromptL supports logic expressions, enabling you to perform calculations or transformations directly in the prompt.

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Simple Expressions

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Conditional Expressions

You can use ternary-like conditions to modify variable values dynamically:

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Advanced Examples

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Combining Input Parameters, Defaults, and Expressions

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Nested or Structured Variables

Variables can represent objects or arrays, making it easy to handle structured data:

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Best Practices

  • Use Clear Variable Names: Choose descriptive names to make your prompts easy to understand.
    • Good: user.name, weather.currentTemp
    • Bad: x, temp
  • Avoid Redefinition: Define variables once and reuse them instead of redefining them unnecessarily.
  • Default Values for Robustness: Use default values to handle missing inputs gracefully.
  • Combine with Logic: Use expressions to preprocess data directly in the prompt, reducing complexity elsewhere.

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Debugging Variables

If a variable isn’t working as expected:
  • Check Scope: Ensure the variable is defined or provided as an input parameter.
  • Validate Expressions: Double-check calculations or transformations.
  • Use Defaults: Add default values to catch undefined variables.

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Summary

Variables in PromptL enable dynamic and reusable prompts. By combining definitions, input parameters, defaults, and expressions, you can create highly flexible and maintainable conversations tailored to any use case.