 The archetypical intensional functions that one is likely to encounter are algorithms. As examples, we might think of various specifications to calculate the decimal expansion of \(\pi\), or various computer programs that behave in the same way. For instance, compilers (for one and the same language) may differ from each other by using or not using some optimizations, and thereby, producing programs from a given piece of code that have identical input–output behavior but different run times.