Inlinesyntax

Inlinesyntax is a design pattern used to embed inline expressions within a host language or text, enabling dynamic content generation at render time. It combines a lightweight parsing mechanism with an evaluation step that inserts computed values directly into the surrounding content.

The pattern relies on delimiters that mark the boundaries of an inline block, a small parser to recognize those blocks, and a defined evaluation context. Inline expressions are typically evaluated when the host content is processed rather than compiled, allowing the same source to produce different results depending on the provided data.

Common forms of inline syntax include curly-brace expressions such as ${expr} found in many scripting and templating contexts, double-brace blocks like {{expr}} used by popular templating engines, and percent-delimited constructs such as <% code %> seen in some preprocessors. While the exact delimiters vary, the core idea remains the same: compute a value within the inline region and substitute it into the surrounding text.

Inlinesyntax is widely used in templates, documentation generators, and code or data generation workflows, where text must incorporate computed values, conditional content, or looping results without introducing separate syntax blocks. Implementations typically specify data access rules, available functions, and how results are inserted back into the host medium.

Key considerations include escaping to prevent unintended interpretation, scoping and security of the evaluation environment, handling of null or missing data, and error reporting. Performance can be affected by the frequency of evaluations and the complexity of expressions, so caching and safe evaluation strategies are common optimizations.

See also: templating, string interpolation, embedded domain-specific languages.