# Evaluation Of Functions - HP -28S Manual

• If a name refers to a program that takes no arguments from the
stack and returns exactly one result, you can use the program's
name to refer (indirectly) to the result. Evaluation of the algebraic
causes execution of the program, so in effect the program's name is
replaced by the result. For examples, see HSummary Statistics
H
on
page 262.
• If a name refers to a second algebraic, evaluation of the first alge-
braic
doesn't
cause evaluation of the second algebraic. Instead, the
second algebraic effectively replaces its name in the first algebraic.
A special case among functions is the function
U=H,
which distin-
guishes equations from expressions. Depending on the Result mode
(Symbolic or Numerical), executing
=
returns an equation or a nu-
merical result.
• In Symbolic Result mode, evaluating an equation produces a new
equation. The new left-hand expression is the result of evaluating
the original left-hand expression. The new right-hand expression is
the result of evaluating the original right-hand expression.
• In Numerical Result mode, evaluating an equation produces the nu-
merical difference between the original left-hand expression (nu-
merically evaluated) and the original right-hand expression
(numerically evaluated).
The next section describes Result modes in more detail.
Evaluation of Functions
When a function is evaluated, its action depends on the current Result
mode, which can be Symbolic or Numerical. These modes are also
described in the next chapter, HModes./I
Symbolic Result Mode. This is the default case, where a function
accepts symbolic arguments and returns symbolic results. The action
of functions in Symbolic Result mode is evident when you calculate
with names and expressions to create larger expressions.
23: Evaluation
203  