Yorick (programming language)

Yorick
Designed by	David H. Munro
First appeared	1996
Stable release	2.2.04 / May 2015
OS	Unix, Linux, Mac, Microsoft Windows
License	BSD
Filename extensions	.i
Website	Yorick Home Page

Yorick is an interpreted programming language designed for numerics, graph plotting, and steering large scientific simulation codes. It is quite fast due to array syntax, and extensible via C or Fortran routines. It was created in 1996 by David H. Munro of Lawrence Livermore National Laboratory.

Features

Indexing

Yorick is good at manipulating elements in N-dimensional arrays conveniently with its powerful syntax.

Several elements can be accessed all at once:

> x=[1,2,3,4,5,6];
> x
[1,2,3,4,5,6]
> x(3:6)
[3,4,5,6]
> x(3:6:2)
[3,5]
> x(6:3:-2)
[6,4]

Arbitrary elements

> x=[[1,2,3],[4,5,6]]
> x
[[1,2,3],[4,5,6]]
> x([2,1],[1,2])
[[2,1],[5,4]]
> list=where(1<x)
> list
[2,3,4,5,6]
> y=x(list)
> y
[2,3,4,5,6]

Pseudo-index

Like "theading" in PDL (Perl Data Language) and "broadcasting" in Numpy (Numeric extension for Python), Yorick has a mechanism to do this:

> x=[1,2,3]
> x
[1,2,3]
> y=[[1,2,3],[4,5,6]]
> y
[[1,2,3],[4,5,6]]
> y(-,)
[[[1],[2],[3]],[[4],[5],[6]]]
> x(-,)
[[1],[2],[3]]
> x(,-)
[[1,2,3]]
> x(,-)/y
[[1,1,1],[0,0,0]]
> y=[[1.,2,3],[4,5,6]]
> x(,-)/y
[[1,1,1],[0.25,0.4,0.5]]

Rubber index

".." is a rubber-index to represent zero or more dimensions of the array.

> x=[[1,2,3],[4,5,6]]
> x
[[1,2,3],[4,5,6]]
> x(..,1)
[1,2,3]
> x(1,..)
[1,4]
> x(2,..,2)
5

"*" is a kind of rubber-index to reshape a slice(sub-array) of array to a vector.

> x(*)
[1,2,3,4,5,6]

Tensor multiplication

Tensor multiplication is done as follows in Yorick:

P(,+,,)*Q(,,+)

means $\sum _{j=1}^{j=N}{P_{ijkl}Q_{mnj}}$

> x=[[1,2,3],[4,5,6]]
> x
[[1,2,3],[4,5,6]]
> y=[[7,8],[9,10],[11,12]]
> x(,+)*y(+,)
[[39,54,69],[49,68,87],[59,82,105]]
> x(+,)*y(,+)
[[58,139],[64,154]]

External links

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