Аннотация:Proof mining is the process of logically analyzing proofs in
mathematics with the aim of obtaining new information. In this survey
paper, we discuss, by means of examples from mathematics, some of the main
techniques used in proof mining. We show that these techniques apply not
only to proofs based on classical logic but also to proofs that involve
noneffective principles such as the attainment of the infimum of $f\in
C[0,1]$ and the convergence for bounded monotone sequences of reals. We
also report on recent case studies in approximation theory and fixed point
theory where new results were obtained.