Composite expressions

Composite expressions are the means by which larger expressions are constructed from smaller expressions. This section describes the composite expressions except for functions, which we discuss in the following section.

Some composite expressions impose restrictions on the possible types of their subexpressions. Specifically, the composite expressions let, if, and sort require subexpressions of a small number of types. Therefore, to simplify the following discussions, use the symbols Π and Σ to stand for the permissible types: Π represents one of string, integer, real, boolean, object, object collection, or string collection, and Σ represents one of string, integer, real, or boolean. The symbol Π is used in the discussion of let and if. The symbol Σ is used in the discussion of sort.


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