Rapid Prototyping vs Product Development
Rapid prototyping: full product specifications typically unavailable. Minor bugs may not be a problem. Programmer time is of the essence. Early semantic feedback emphasized above thorough error checking. High-level features (e.g., garbage collection, infinite-precision integers) that remove burdens from the programmer are prominent, even if they slow performance.
Product development: product specification is complete or almost complete. Bugs will be highly embarrassing or worse. Compilers with strict type checking and the use of test protocols are prominent. Correct adherence to spec is very important, as is maintainability of code. Code optimization for performance is often an issue.