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opal    音标拼音: ['opəl]
n. 蛋白石,猫眼石

蛋白石,猫眼石

opal
n 1: a translucent mineral consisting of hydrated silica of
variable color; some varieties are used as gemstones

Opal \O"pal\, n. [L. opalus: cf. Gr. ?, Skr. upala a rock,
stone, precious stone: cf. F. opale.] (Min.)
A mineral consisting, like quartz, of silica, but inferior to
quartz in hardness and specific gravity.
[1913 Webster]

Note: The {precious opal} presents a peculiar play of colors
of delicate tints, and is highly esteemed as a gem. One
kind, with a varied play of color in a reddish ground,
is called the {harlequin opal}. The {fire opal} has
colors like the red and yellow of flame. {Common opal}
has a milky appearance. {Menilite} is a brown impure
variety, occurring in concretions at Menilmontant, near
Paris. Other varieties are {cacholong}, {girasol},
{hyalite}, and {geyserite}.
[1913 Webster]

1. A {DSP} language.

["OPAL: A High Level Language and Environment for DSP boards
on PC", J.P. Schwartz et al, Proc ICASSP-89, 1989].

2. The language of the {object-oriented database} {GemStone}.

["Making Smalltalk a Database System", G. Copeland et al, Proc
SIGMOD'84, ACM 1984, pp.316- 325].

3. A {simulation} language with provision for {stochastic
variables}. An extension of {Autostat}.

["C-E-I-R OPAL", D. Pilling, Internal Report,
C.E.I.R. Ltd. (1963)].

4. A language for compiler testing said to be used internally
by {DEC}.

5. A {functional programming} language designed at the
{Technische Universitaet Berlin} as a testbed for the
development of {functional programs}. OPAL integrates
concepts from Algebraic Specification and Functional
Programming, which favour the (formal) development of (large)
production-quality software written in a {purely functional}
style.

The core of OPAL is a {strongly typed}, {higher-order},
{strict} applicative language which belongs to the tradition
of {Hope} and {ML}. The algebraic flavour of OPAL is visible
in the syntactical appearance and in the preference of
{parameterisation} to {polymorphism}.

OPAL supports: {information hiding} - each language unit is
divided into an interface (signature) and an implementation
part; selective import; {parameterised modules}; free
constructor {views} on {sorts}, which allow pattern-based
function definitions despite quite different implementations;
full {overloading} of names; puristic scheme language with no
{built-in} data types (except {Booleans} and denotations).

OPAL and its predecessor OPAL-0 have been used for some time
at the Technische Universitaet Berlin in CS courses and for
research into optimising compilers for applicative languages.
The OPAL compiler itself is writte entirely in OPAL.

An overview is given in "OPAL: Design And Implementation of an
Algebraic Programming Language".

{(http://cs.tu-berlin.de/~opal/)}.

{(ftp://ftp.cs.tu-berlin.de/pub/local/uebb/papers/DesignImplOpal.ps.gz)}.

(1995-02-16)

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  • Opal - Wikipedia
    For use in jewellery, most opal is cut and polished to form a cabochon, a convex shape that maximises the viewing angles through which an opal's play of colour can be observed "Natural" opal refers to polished stones consisting wholly of precious opal
  • Opal [Experiment]
    Opal [Experiment]
  • Pictures of Opal - Black, Fire, Boulder, Blue and Pink
    Photos of opal from around the world Guidance for people who want to buy opal, see different types of opal, understand their names, learn about synthetics and imitations
  • Opal Gemstone | Opal Stone – GIA
    Opal is the product of seasonal rains that drenched dry ground in regions such as Australia’s semi-desert “Outback ” It is known for its unique display of flashing rainbow colors
  • Opal | Properties, Types Uses | Britannica
    Opal, silica mineral extensively used as a gemstone, a submicrocrystalline variety of cristobalite In ancient times opal was included among the noble gems and was ranked second only to emerald by the Romans
  • Opal Gems: Value, Price, and Jewelry Information - IGS
    Opal gems are so unique you’ll need a special vocabulary to describe them Learn all about the many opal varieties and how to evaluate them
  • Opal - International Colored Gemstone Association
    October’s birthstone, opal is a gem of positive transformation, revealing the colorful attributes of those who wear it Magical, mysterious, and lively—opal is captivating new admirers with its variety
  • Opal : Properties, Formation, Uses and Deposits - Geology Science
    Definition: Opals are a type of mineraloid, which means they lack the crystalline structure of typical minerals Instead, opals are composed of tiny spheres of silica, often arranged in a closely packed and orderly manner What sets opals apart from other gemstones is their remarkable play of color, which is a phenomenon known as “opalescence ”
  • Opal Gemstones: History, Symbolism, Meanings More
    Opals are a hydrated silica gemstone seen in a stunning array of vibrant colors and patterns Learn why no two opal gemstones are the same, and the meaning, history, and details that make them highly desired!
  • Opal: The mineral Opal (black, white, fire) information and pictures
    For this reason, Opal is one of the most fascinating and fabled of gemstones Opal, being amorphous, is not truly a mineral but a mineraloid One of the scientifically accepted standards defining a mineral is that a mineral must have a crystal structure, which opal lacks





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