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In [[A Programming Language]], prefix and suffix operations were described using the syntax <math>\alpha^j/x</math> to take the first <math>j</math> elements of vector <math>x</math> and <math>\omega^j/x</math> for the last <math>j</math> elements. This combined a use of the special prefix and suffix vectors <math>\alpha^j(n)</math> and <math>\omega^j(n)</math> with [[Compress|compression]], with the length <math>n</math> inferred based on the length of <math>x</math>. The symbol <math>↑</math> was used for vector [[Rotate]], while <math>↓</math> rotated in the opposite direction.<ref>Iverson, K.E. (1962). A Programming Language. Wiley. ISBN 978-0-471-43014-8.</ref> | In [[A Programming Language]], prefix and suffix operations were described using the syntax <math>\alpha^j/x</math> to take the first <math>j</math> elements of vector <math>x</math> and <math>\omega^j/x</math> for the last <math>j</math> elements. This combined a use of the special prefix and suffix vectors <math>\alpha^j(n)</math> and <math>\omega^j(n)</math> with [[Compress|compression]], with the length <math>n</math> inferred based on the length of <math>x</math>. The symbol <math>↑</math> was used for vector [[Rotate]], while <math>↓</math> rotated in the opposite direction.<ref>Iverson, K.E. (1962). A Programming Language. Wiley. ISBN 978-0-471-43014-8.</ref> | ||
The first version of [[APL\360]]<ref>Falkoff, A.D., and K.E. Iverson. [https://www.jsoftware.com/papers/APL360TerminalSystem.htm "The APL\360 Terminal System"]. Research Report RC-1922, IBM, 1967-10-16.</ref> followed Iverson notation in defining prefix and suffix vectors but not Take, even though the arrow symbols were no longer used for Rotate. For a vector <source lang=apl inline>x</source>, what is now <source lang=apl inline>j↑x</source> would have been written <source lang=apl inline>(j⍺(⍴x))/x</source> while <source lang=apl inline>(-j)↑x</source> would be <source lang=apl inline>(j⍵(⍴x))/x</source>. The functions Take and Drop using arrow symbols were introduced by 1968<ref>Falkoff, A.D., and K.E. Iverson, "[http://keiapl.org/archive/APL360_UsersMan_Aug1968.pdf APL\360 User's Manual]". IBM, August 1968.</ref>. | |||
The [[Function axis|axis]] specification for Take was defined in [[APL2]]. It is shared by [[SHARP APL]] and [[Rationalized APL]], and continues to be supported in [[Dyalog APL]]. | The [[Function axis|axis]] specification for Take was defined in [[APL2]]. It is shared by [[SHARP APL]] and [[Rationalized APL]], and continues to be supported in [[Dyalog APL]]. | ||