Similar rules apply for the use of function calls in expressions as for the use of variable names. Instead of the function name being inserted in the calculation of the expression, the result that is returned by the function thus called is inserted.
For a description of how functions are called and which functions are available in structured procedures, see chapter “Functions”.
The result of the function can have the data type INTEGER, BOOLEAN or STRING, i.e. it can be a number, a Boolean value or a string. Consequently, the rules that apply to function results are the same as those described in preceding sections for numbers, Boolean constants and strings.
If the result of the function call is to be evaluated, the function call must not be enclosed in single quotes. If it is enclosed in single quotes, the function name is interpreted as a string.
If variables and functions have the same name, the variable is evaluated in accordance with the rules for S procedures. Any confusion can be avoided by specifying the identifying parentheses in the function call.