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

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bc
Usage notes
Files
Localization
1. Unlike the C language, which uses lexical scoping rules, bc uses dynamic
scoping, which is most easily explained with an example:
a=10
define f1() {
auto a;
a = 13;
return (f2())
}
define f2() {
return (a)
}
f1()
13
f2()
10
If f1() is called, bc prints the number 13, instead of the number 10. This is
because f1() hides away the old (global) value of a and then sets it to 13. When
f2() refers to a, it sees the variable dynamically created by f1() and so prints 13.
When f1() returns, it restores the old value of a. When f2() is called directly,
instead of through f1(), it sees the global value for a and prints 10. The
corresponding C code prints 10 in both cases.
2. Numbers are stored as strings in the program and converted into numbers each
time they are used. This is important because the value of a “constant” number
may change depending on the setting of the ibase variable. For example,
suppose the following instructions are given to bc:
define ten() {
return (10)
}
ten()
10
ibase=16
ten()
16
In this example, when the base is set to 10, ten() returns the decimal value 10.
However, when the input base is changed to 16, the function returns the
decimal value 16. This can be a source of confusing errors in bc programs.
3. The library of functions loaded using the –l option is stored in the file
/usr/lib/lib.b under your root directory. This is a simple text file that you can
examine and change to add new functions as desired.
4. In a noninteractive invocation, bc will exit on any invalid input and the rest of
the input will be skipped.
bc uses the following file:
/usr/lib/lib.b
File containing the library of functions loaded with –l
bc uses the following localization environment variables:
v LANG
v LC_ALL
v LC_CTYPE
v LC_MESSAGES
v LC_SYNTAX
64 z/OS V1R9.0 UNIX System Services Command Reference