Eval
eval is a language operation or built-in function that interprets and executes a code representation within a specified execution context.
The Well-Grounded Rubyist, Fourth Edition
eval is a Ruby method that parses and executes Ruby code supplied as a string within a specified execution context.
- How it is used
- Uses runtime string evaluation for dynamic expressions, method creation, method invocation, and execution within captured local-variable contexts.
- How deep it goes
- Explains direct execution, Binding-based scope resolution, related eval methods, and security hazards without detailing parser or VM internals.
- Examples
- Demonstrates arithmetic evaluation, dynamically named methods, and access to a top-level local variable through binding.
- What you can do after
- Evaluate/understand how Ruby executes code strings, supplies bindings, and exposes dangerous injection paths.
Read how The Well-Grounded Rubyist, Fourth Edition explains eval →
Python How-To
eval is Python's built-in function that evaluates a string or code object as a Python expression and returns its result.
- How it is used
- Uses eval to recover Python data represented by strings during text processing.
- How deep it goes
- Explains string evaluation, iterable pitfalls, syntax errors, and security risks, but does not develop evaluation internals.
- Examples
- Demonstrates list, tuple, and dictionary strings, constructor failures, malformed syntax, and manual comma-separated parsing.
- What you can do after
- Apply it via Python's built-in eval to trusted strings representing Python expressions.
Related concepts
- dynamic evaluationimplements · Dynamic evaluation is runtime evaluation in which executable content or decision criteria are determined from current values or context.
- instance_evalincludes · instance_eval is a Ruby method that evaluates code in the context of a specified object, temporarily changing self to that object.
- JSON.parsealternative to · JSON.parse is a standard JavaScript function that parses a JSON-formatted string into the corresponding JavaScript value.
- quantitative dataproduces · Quantitative data is information represented numerically as quantities, measurements, counts, or other values suitable for numerical interpretation or analysis.
- untrusted inputused by · Untrusted input is externally supplied data or content whose safety, integrity, or reliability has not been established for its processing context.
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