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f (1,2);
5
For more complicated functions, the procedure statement can be used. Its syntax is:
proc (name-sequence)
local name-sequence;
global name-sequence;
options name-sequence;
statement-sequence;
end;
The proc (name-sequence) is the procedure header, and the name-sequence is a formal parameter
list. These are the internal variable names for values that you would pass during calls to the
procedure. The global and local name-sequence are optional clauses listing the global and local
variables, and options name-sequence is an optional clause of settings that influence the procedure's
behaviour at runtime.
Notice that there is no specification for the name of the procedure. Since procedures are objects that
can be assigned to variables, the name of the variable you assign it to is used as the name of
procedure. The value of the procedure is usually the value of the last expression evaluated. Other
values may be returned by using explicit return, error return, or return through a parameter. See the
Maple V Programming Guide for more information on return types.
Example:
> # Out of curiosity, see if "x" is a mathematical
variable:
> x;
x
> f := proc(x)
> x^2 + 1;
> end;
f := proc(x) x^2+1 end
> f(2);
5
> x;
x
In this example, the global variable "x" is not affected by the formal parameter "x", which is local to
function "f".
11.6.2.1 Local Variables
In addition to global variables, local variables may be used in procedures to make temporary
assignments without affecting the rest of the Maple session. Changing the value of a local variable in a
procedure does not affect the value of a variable with the same name in another procedure, or of a
global variable of the same name. Changing the value of a global variable changes it for the entire
Maple session.
Local variables also have one other very important distinction: they are not subject to the default full
evaluation. This is because local variables commonly do not require full evaluation, so performance is
improved by this exception to the general evaluation scheme.
Example:
> # Set value of global "a":
> a := 0;
a := 0
> g := proc(x)
> local a, b;
> a := b^2 + x;
> print(a);
122