Calcium strontium or barium, the oxide–nitride coating that results in air is stable and lathe machining and other standard metallurgical techniques are suitable for calcium. In the United States and Canada, calcium is instead produced by reducing lime with aluminium at high temperatures. Calcium provides a link between tectonics, climate, and the carbon cycle. In the simplest terms, uplift of mountains exposes calcium-bearing rocks to chemical weathering and releases Ca into surface water. These ions are transported to the ocean where they react with dissolved CO to form limestone (), which in turn settles to the sea floor where it is
Symbol table global scope, whether it is imported, and what namespace it belongs to. Some programming languages allow the symbol table to be manipulated at run-time, so that symbols can be added at any time. Racket is an example of such a language. Both the LISP and the Scheme programming languages allow arbitrary, generic properties to be associated with each symbol. The Prolog programming language is essentially a symbol-table manipulation language; symbols are called "atoms", and the relationships between symbols can be reasoned over. Similarly, OpenCog provides a dynamic symbol table, called the "atomspace", which is used for knowledge representation. Symbol table