Formulae nesting order

Uses of cnclii,sinj> murks. The formula for the entire coordination enlily. whether charged or not. is enclosed in square brackets. When ligands are polyatomic, their formulae are enclosed in parentheses. Ligand abbreviations are also enclosed in parentheses. In the special case of coordination entities, the nesting order of enclosures is as given [on page A-5I. There should be no space between representations of ionic species within a coordination formula. 

In formulae, these enclosing marks are used in the following nesting order [],[()],[ () ], [( () )], [ ( () ) ], etc. Square brackets are normally used only to enclose entire formulae parentheses and braces are then used alternately (see also Sections IR-4.2.3 and IR-9.2.3.2). There are, however, some specific uses of square brackets in formulae, cf. Section IR-2.2.2.1. 

Data stored in a stack are accessible to the program in the reverse of the input order, a property that is useful in situations involving recursion. Evaluating an algebraic formula involving nested expressions is a recursive process that is facilitated by use of a stack to store left parentheses and symbols (operands) while the program interprets operators. 

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