Procrustes (Προκρούστης) "the stretcher", also known as Damastes (Δαμαστής) "subduer" and Polypaemon Πολυπαίμων "harming much", is a figure from Greek mythology. He was a bandit from Attica, with a stronghold in the hills outside Eleusis. There, he had an iron bed into which he invited every passerby to lie down. If the guest proved too tall, he would amputate the excess length; victims who were too short were stretched on the rack until they were long enough. Nobody ever fit in the bed because it was secretly adjustable: Procrustes would stretch or shrink it upon sizing his victims from afar. Procrustes continued his reign of terror until he was captured by Theseus, who "fitted" Procrustes to his own bed and cut off his head and feet (since Theseus was a stout fellow, the bed had been set on the short position). Killing Procrustes was the last adventure of Theseus on his journey from Troezen to Athens.
A Procrustean bed is an arbitrary standard to which exact conformity is forced. Sometimes the term is applied to the pan and scan process of cropping motion pictures for television and home video. It is also a term popular with students, when lamenting essays of a fixed page length.
Procrustes analysis is the name for the process of performing a shape-preserving Euclidean transformation to a set of shapes. This removes variations in translation, rotation and scaling across the dataset in order to move them into a common frame of reference. This is generally the precursor to further statistical analysis. A related problem in linear algebra is the orthogonal Procrustes problem of finding the closest orthogonal matrix to any given matrix.
In computer science, a Procrustean string is a fixed length string into which strings of varying lengths are placed. If the string inserted is too short, then it is padded out, usually with spaces or null characters. If the string inserted is too long, it is truncated. The concept is mentioned in the Sinclair ZX81 user manual, where a portion of a string is replaced by another string using Procrustean assignment — the replacement string is truncated or padded in order to have length equal to the portion being replaced.. Although the term did not catch on in wider usage, it appears in some references, notably FOLDOC.
In 1959 science fiction novel Eden by Stanisław Lem, Procrustics is the name of a fictitious information-theory based social engineering discipline of molding groups within a society and ultimately a society as a whole to behave as designed by secretive hidden rulers, to create a hideous form of social control in which the very existence of the governing powers is denied and individuals appear to themselves to be free yet are being manipulated and controlled. One example described in the novel is "concentration camps" without any guards which are designed so that the prisoners stay inside apparently on their "free" will.
In Webster v. Reproductive Health Services a Supreme Court plurality likened the use of the trimester framework for determining the Constitutionality of a government regulation of abortion to the application of a Procrustean Bed.