z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

c
Each parameter on the first line can be a variable name or an array name. Array
names are indicated by putting square brackets after them. For example, if cmpvec
is a function that compares two vectors, the function definition might start with:
define cmpvec(a[],b[]) {
Parameters do not conflict with arrays or variables of the same name. For example,
you can have a parameter named a inside a function, and a variable named a
outside, and the two are considered entirely separate entities. Assigning a value to
the variable does not change the parameter and vice versa. All parameters are
passed by value. This means that a copy is made of the argument value and is
assigned to the formal parameter. This also applies to arrays. If you pass an array
to a function, a copy is made of the whole array, so any changes made to the array
parameter do not affect the original array.
A function may not need any arguments. In this case, the define line does not have
any parameters inside the parentheses, as in:
define f() {
The auto statement declares a sequence of local variables. When a variable or
array name appears in an auto statement, the current values of those items are
saved and the items are initialized to zero. For the duration of the function, the
items have their new values. When the function ends, the old values of the items
are restored.
However, bc uses dynamic scoping rules, unlike C which uses lexical scoping rules.
See Usage notes for more details.
For example:
define addarr(a[],l) {
auto i, s
for (i=0; i < l; ++i) s += a[i]
return (s)
}
is a function that adds the elements in an array. The argument l stands for the
number of elements in the array. The function uses two local names: a variable
named i and a variable named s. These variables are “local” to the function addarr
and are unrelated to objects of the same name outside the function (or in other
functions). Objects that are named in an auto statement are called autos. Autos are
initialized to 0 each time the function is called. Thus, the sum s is set to zero each
time this function is called. You can also have local arrays, which are specified by
placing square brackets after the array name in the auto statement.
define func_with_local_array() {
auto local_array[];
for(i=0; i