NAME
bc —
arbitrary precision calculator
language
SYNOPSIS
bc |
[-hilqsvw]
[long-options]
[file ...] |
DESCRIPTION
bc is a language that supports arbitrary precision numbers
with interactive execution of statements. There are some similarities in the
syntax to the C programming language. A standard math library is available by
command line option. If requested, the math library is defined before
processing any files.
bc starts by processing code from all
the files listed on the command line in the order listed. After all files have
been processed,
bc reads from the standard input. All code
is executed as it is read. (If a file contains a command to halt the
processor,
bc will never read from the standard input.)
This version of
bc contains several extensions beyond
traditional
bc implementations and the POSIX draft standard.
Command line options can cause these extensions to print a warning or to be
rejected. This document describes the language accepted by this processor.
Extensions will be identified as such.
OPTIONS
-
-
- -h,
--help
- Print the usage and exit.
-
-
- -i,
--interactive
- Force interactive mode.
-
-
- -l,
--mathlib
- Define the standard math library.
-
-
- -q,
--quiet
- Quiet mode.
-
-
- -s,
--standard
- Process exactly the POSIX bc
language.
-
-
- -v,
--version
- Print the version number and copyright and quit.
-
-
- -w,
--warn
- Give warnings for extensions to POSIX
bc.
NUMBERS
The most basic element in
bc is the number. Numbers are
arbitrary precision numbers. This precision is both in the integer part and
the fractional part. All numbers are represented internally in decimal and all
computation is done in decimal. (This version of
bc
truncates results from divide and multiply operations.) There are two
attributes of numbers, the length and the scale. The length is the total
number of significant decimal digits in a number and the scale is the total
number of decimal digits after the decimal point. For example:
.000001 has a length of 6 and scale of 6.
1935.000 has a length of 7 and a scale of 3.
VARIABLES
Numbers are stored in two types of variables, simple variables and arrays. Both
simple variables and array variables are named. Names begin with a letter
followed by any number of letters, digits and underscores. All letters must be
lower case. (Full alpha-numeric names are an extension. In POSIX
bc all names are a single lower case letter.) The type of
variable is clear by the context because all array variable names will be
followed by brackets ([]).
There are four special variables,
scale,
ibase,
obase, and
last.
scale defines how some operations use digits after the
decimal point. The default value of
scale is 0.
ibase and
obase define the conversion base
for input and output numbers. The default for both input and output is base
10.
last (an extension) is a variable that has the value of
the last printed number. These will be discussed in further detail where
appropriate. All of these variables may have values assigned to them as well
as used in expressions.
Comments in
bc start with the characters
“
/*” and end with the characters
“
*/”. Comments may start anywhere and appear as
a single space in the input. (This causes comments to delimit other input
items. For example, a comment can not be found in the middle of a variable
name.) Comments include any newlines (end of line) between the start and the
end of the comment.
To support the use of scripts for
bc, a single line comment
has been added as an extension. A single line comment starts at a
“
#” character and continues to the next end of
the line. The end of line character is not part of the comment and is
processed normally.
EXPRESSIONS
The numbers are manipulated by expressions and statements. Since the language
was designed to be interactive, statements and expressions are executed as
soon as possible. There is no “main” program. Instead, code is
executed as it is encountered. (Functions, discussed in detail later, are
defined when encountered.)
A simple expression is just a constant.
bc converts constants
into internal decimal numbers using the current input base, specified by the
variable
ibase. (There is an exception in functions.) The
legal values of
ibase are 2 through 36. (Base values greater
than 16 are an extension.) Assigning a value outside this range to
ibase will result in a value of 2 or 36. Input numbers may
contain the characters 0-9 and A-Z. (Note: They must be capitals. Lower case
letters are variable names.) Single digit numbers always have the value of the
digit regardless of the value of
ibase. (i.e. A = 10.) For
multi-digit numbers,
bc changes all input digits greater or
equal to ibase to the value of
ibase - 1. This makes the
number “ZZZ” always be the largest 3 digit number of the input
base.
Full expressions are similar to many other high level languages. Since there is
only one kind of number, there are no rules for mixing types. Instead, there
are rules on the scale of expressions. Every expression has a scale. This is
derived from the scale of original numbers, the operation performed and in
many cases, the value of the variable
scale. Legal values of
the variable
scale are 0 to the maximum number representable
by a C integer.
In the following descriptions of legal expressions, “expr” refers to
a complete expression and “var” refers to a simple or an array
variable. A simple variable is just a
name and an array
variable is specified as
name[expr]. Unless specifically
mentioned the scale of the result is the maximum scale of the expressions
involved.
-
-
- -
expr
- The result is the negation of the expression.
-
-
- ++
var
- The variable is incremented by one and the new value is the
result of the expression.
-
-
- --
var
- The variable is decremented by one and the new value is the
result of the expression.
-
-
- var
++
- The result of the expression is the value of the variable
and then the variable is incremented by one.
-
-
- var
--
- The result of the expression is the value of the variable
and then the variable is decremented by one.
-
-
- expr +
expr
- The result of the expression is the sum of the two
expressions.
-
-
- expr -
expr
- The result of the expression is the difference of the two
expressions.
-
-
- expr *
expr
- The result of the expression is the product of the two
expressions.
-
-
- expr /
expr
- The result of the expression is the quotient of the two
expressions. The scale of the result is the value of the variable
scale.
-
-
- expr %
expr
- The result of the expression is the remainder and it is
computed in the following way: To compute a%b, first a/b is computed to
scale digits. That result is used to compute a-(a/b)*b
to the scale of the maximum of scale + scale(b) and
scale(a). If scale is set to zero and both expressions
are integers this expression is the integer remainder function.
-
-
- expr ^
expr
- The result of the expression is the value of the first
raised to the second. The second expression must be an integer. (If the
second expression is not an integer, a warning is generated and the
expression is truncated to get an integer value.) The scale of the result
is scale if the exponent is negative. If the exponent is
positive, the scale of the result is the minimum of the scale of the first
expression times the value of the exponent and the maximum of
scale and the scale of the first expression. (e.g.
scale(a^b) = min(scale(a)*b, max( scale, scale(a))).) It
should be noted that expr^0 will always return the value of 1.
-
-
- ( expr
)
- This alters the standard precedence to force the evaluation
of the expression.
-
-
- var =
expr
- The variable is assigned the value of the expression.
-
-
- var
<op>= expr
- This is equivalent to var = var <op>
expr with the exception that the “var”
part is evaluated only once. This can make a difference if
“var” is an array.
Relational expressions are a special kind of expression that always evaluate to
0 or 1, 0 if the relation is false and 1 if the relation is true. These may
appear in any legal expression. (POSIX
bc requires that
relational expressions are used only in
if,
while, and
for statements and that only
one relational test may be done in them.) The relational operators are:
-
-
- expr1 <
expr2
- The result is 1 if expr1 is strictly less than expr2.
-
-
- expr1 <=
expr2
- The result is 1 if expr1 is less than or equal to
expr2.
-
-
- expr1 >
expr2
- The result is 1 if expr1 is strictly greater than
expr2.
-
-
- expr1 >=
expr2
- The result is 1 if expr1 is greater than or equal to
expr2.
-
-
- expr1 ==
expr2
- The result is 1 if expr1 is equal to expr2.
-
-
- expr1 !=
expr2
- The result is 1 if expr1 is not equal to expr2.
Boolean operations are also legal. (POSIX
bc does
NOT have boolean operations.) The result of all boolean
operations are 0 and 1 (for false and true) as in relational expressions. The
boolean operators are:
-
-
- !expr
- The result is 1 if expr is 0.
-
-
- expr
&& expr
- The result is 1 if both expressions are non-zero.
-
-
- expr ||
expr
- The result is 1 if either expression is non-zero.
The expression precedence is as follows: (lowest to highest)
- || operator, left associative
- && operator, left associative
- ! operator, nonassociative
- Relational operators, left associative
- Assignment operator, right associative
- + and - operators, left associative
- *, / and % operators, left associative
- ^ operator, right associative
- unary - operator, nonassociative
- ++ and -- operators, nonassociative
This precedence was chosen so that POSIX compliant
bc programs
will run correctly. This will cause the use of the relational and logical
operators to have some unusual behavior when used with assignment expressions.
Consider the expression:
a = 3 < 5
Most C programmers would assume this would assign the result of
“
3 < 5” (the value 1) to the variable
“
a”. What this does in
bc is
assign the value 3 to the variable “
a” and then
compare 3 to 5. It is best to use parenthesis when using relational and
logical operators with the assignment operators.
There are a few more special expressions that are provided in
bc. These have to do with user defined functions and
standard functions. They all appear as “
name
(
parameters)”. See the section on functions for
user defined functions. The standard functions are:
-
-
- length
(expression)
- The value of the length function is the number of
significant digits in the expression.
-
-
- read
()
- The read function (an extension) will read a number from
the standard input, regardless of where the function occurs. Beware, this
can cause problems with the mixing of data and program in the standard
input. The best use for this function is in a previously written program
that needs input from the user, but never allows program code to be input
from the user. The value of the read function is the number read from the
standard input using the current value of the variable
ibase for the conversion base.
-
-
- scale
(expression)
- The value of the scale function is the number of digits
after the decimal point in the expression.
-
-
- sqrt
(expression)
- The value of the sqrt function is the square root of the
expression. If the expression is negative, a run time error is
generated.
STATEMENTS
Statements (as in most algebraic languages) provide the sequencing of expression
evaluation. In
bc statements are executed “as soon as
possible”. Execution happens when a newline in encountered and there is
one or more complete statements. Due to this immediate execution, newlines are
very important in
bc. In fact, both a semicolon and a
newline are used as statement separators. An improperly placed newline will
cause a syntax error. Because newlines are statement separators, it is
possible to hide a newline by using the backslash character. The sequence
“
\<nl>”, where <nl> is the newline
appears to
bc as whitespace instead of a newline. A
statement list is a series of statements separated by semicolons and newlines.
The following is a list of
bc statements and what they do:
(Things enclosed in brackets ([]) are optional parts of the statement.)
-
-
- expression
- This statement does one of two things. If the expression
starts with ⟨variable⟩
⟨assignment⟩ ..., it is considered to
be an assignment statement. If the expression is not an assignment
statement, the expression is evaluated and printed to the output. After
the number is printed, a newline is printed. For example,
“a=1” is an assignment statement and
“(a=1)” is an expression that has an
embedded assignment. All numbers that are printed are printed in the base
specified by the variable obase. The legal values for
obase are 2 through
BC_BASE_MAX
.
(See the section LIMITS.) For bases 2
through 16, the usual method of writing numbers is used. For bases greater
than 16, bc uses a multi-character digit method of
printing the numbers where each higher base digit is printed as a base 10
number. The multi-character digits are separated by spaces. Each digit
contains the number of characters required to represent the base ten value
of “obase-1”. Since numbers are of arbitrary
precision, some numbers may not be printable on a single output line.
These long numbers will be split across lines using the “\” as
the last character on a line. The maximum number of characters printed per
line is 70. Due to the interactive nature of bc,
printing a number causes the side effect of assigning the printed value to
the special variable last. This allows the user to
recover the last value printed without having to retype the expression
that printed the number. Assigning to last is legal and
will overwrite the last printed value with the assigned value. The newly
assigned value will remain until the next number is printed or another
value is assigned to last. (Some installations may allow
the use of a single period (.) which is not part of a number as a short
hand notation for last.)
-
-
- string
- The string is printed to the output.
Strings start with a double quote character and contain all characters
until the next double quote character. All characters are take literally,
including any newline. No newline character is printed after the
string.
-
-
- print
list
- The print statement (an extension)
provides another method of output. The list is a
list of strings and expressions separated by commas. Each string or
expression is printed in the order of the list. No terminating newline is
printed. Expressions are evaluated and their value is printed and assigned
to the variable last. Strings in the
print statement are printed to the output and may
contain special characters. Special characters start with the backslash
character (\). The special characters recognized by bc
are ‘a’ (alert or bell), ‘b’ (backspace),
‘f’ (form feed), ‘n’ (newline), ‘r’
(carriage return), ‘q’ (double quote), ‘t’ (tab),
and ‘\’ (backslash). Any other character following the
backslash will be ignored.
-
-
- {
statement_list }
- This is the compound statement. It allows multiple
statements to be grouped together for execution.
-
-
- if
(expression) statement1
[else statement2]
- The if statement evaluates the
expression and executes
statement1 or statement2
depending on the value of the expression. If the
expression is non-zero,
statement1 is executed. If
statement2 is present and the value of the
expression is 0, then
statement2 is executed. (The else
clause is an extension.)
-
-
- while
(expression) statement
- The while statement will execute the
statement while the expression
is non-zero. It evaluates the expression before each
execution of the statement. Termination of the loop
is caused by a zero expression value or the
execution of a break statement.
-
-
- for
([expression1]; [expression2];
[expression3]) statement
- The for statement controls repeated
execution of the statement.
Expression1 is evaluated before the loop.
Expression2 is evaluated before each execution of
the statement. If it is non-zero, the
statement is evaluated. If it is zero, the loop is
terminated. After each execution of the statement,
expression3 is evaluated before the reevaluation of
expression2. If expression1 or
expression3 are missing, nothing is evaluated at the
point they would be evaluated. If expression2 is
missing, it is the same as substituting the value 1 for
expression2. (The optional expressions are an
extension. POSIX bc requires all three expressions.) The
following is equivalent code for the for statement:
expression1;
while (expression2) {
statement;
expression3;
}
-
-
- break
- This statement causes a forced exit of the most recent
enclosing while statement or for
statement.
-
-
- continue
- The continue statement (an extension)
causes the most recent enclosing for statement to start
the next iteration.
-
-
- halt
- The halt statement (an extension) is an
executed statement that causes the bc processor to quit
only when it is executed. For example,
if (0 == 1) halt
will not cause bc to terminate because the halt is not
executed.
-
-
- return
- Return the value 0 from a function. (See the section on
functions.)
-
-
- return
(expression)
- Return the value of the expression from a function. (See
the section on functions.) As an extension, the parenthesis are not
required.
PSEUDO STATEMENTS
These statements are not statements in the traditional sense. They are not
executed statements. Their function is performed at "compile" time.
-
-
- limits
- Print the local limits enforced by the local version of
bc This is an extension.
-
-
- quit
- When the quit statement is read, the
bc processor is terminated, regardless of where the quit
statement is found. For example,
if (0 == 1) quit
will cause bc to terminate.
-
-
- warranty
- Print a longer warranty notice. This is an extension.
FUNCTIONS
Functions provide a method of defining a computation that can be executed later.
Functions in
bc always compute a value and return it to the
caller. Function definitions are "dynamic" in the sense that a
function is undefined until a definition is encountered in the input. That
definition is then used until another definition function for the same name is
encountered. The new definition then replaces the older definition. A function
is defined as follows:
define name ( parameters ) { newline
auto_list statement_list }
A function call is just an expression of the form
“
name (
parameters)”.
Parameters are numbers or arrays (an extension). In the function definition,
zero or more parameters are defined by listing their names separated by
commas. All parameters are call by value parameters. Arrays are specified in
the parameter definition by the notation “
name
[]”. In the function call, actual parameters are full expressions for
number parameters. The same notation is used for passing arrays as for
defining array parameters. The named array is passed by value to the function.
Since function definitions are dynamic, parameter numbers and types are
checked when a function is called. Any mismatch in number or types of
parameters will cause a runtime error. A runtime error will also occur for the
call to an undefined function.
The
auto_list is an optional list of variables that are
for "local" use. The syntax of the auto list (if present) is
“
auto name,
...;”. (The semicolon is optional.) Each
name is the name of an auto variable. Arrays may be
specified by using the same notation as used in parameters. These variables
have their values pushed onto a stack at the start of the function. The
variables are then initialized to zero and used throughout the execution of
the function. At function exit, these variables are popped so that the
original value (at the time of the function call) of these variables are
restored. The parameters are really auto variables that are initialized to a
value provided in the function call. Auto variables are different than
traditional local variables because if function A calls function B, B may
access function A's auto variables by just using the same name, unless
function B has called them auto variables. Due to the fact that auto variables
and parameters are pushed onto a stack,
bc supports
recursive functions.
The function body is a list of
bc statements. Again,
statements are separated by semicolons or newlines. Return statements cause
the termination of a function and the return of a value. There are two
versions of the return statement. The first form,
“
return”, returns the value 0 to the calling
expression. The second form, “
return
(
expression)”, computes the value of the
expression and returns that value to the calling expression. There is an
implied “
return (
0)” at the
end of every function. This allows a function to terminate and return 0
without an explicit return statement.
Functions also change the usage of the variable
ibase. All
constants in the function body will be converted using the value of
ibase at the time of the function call. Changes of
ibase will be ignored during the execution of the function
except for the standard function
read, which will always use
the current value of
ibase for conversion of numbers.
Several extensions have been added to functions. First, the format of the
definition has been slightly relaxed. The standard requires the opening brace
be on the same line as the
define keyword and all other
parts must be on following lines. This version of
bc will
allow any number of newlines before and after the opening brace of the
function. For example, the following definitions are legal.
define d (n) { return (2*n); }
define d (n)
{ return (2*n); }
Functions may be defined as
void. A
void
funtion returns no value and thus may not be used in any place that needs a
value. A
void function does not produce any output when
called by itself on an input line. The key word
void is
placed between the key word
define and the function name.
For example, consider the following session.
define py (y) { print "--->", y, "<---", "0; }
define void px (x) { print "--->", x, "<---", "0; }
py(1)
--->1<---
0
px(1)
--->1<---
Since
py is not a void function, the call of
py (
1) prints the desired output
and then prints a second line that is the value of the function. Since the
value of a function that is not given an explicit return statement is zero,
the zero is printed. For
px (
1),
no zero is printed because the function is a void function.
Also, call by variable for arrays was added. To declare a call by variable
array, the declaration of the array parameter in the function definition looks
like “
name []”. The call to the function
remains the same as call by value arrays.
MATH LIBRARY
If
bc is invoked with the
-l option, a math
library is preloaded and the default scale is set to 20. The math functions
will calculate their results to the scale set at the time of their call. The
math library defines the following functions:
-
-
- s
(x)
- The sine of x, x is in radians.
-
-
- c
(x)
- The cosine of x, x is in radians.
-
-
- a
(x)
- The arctangent of x, arctangent returns radians.
-
-
- l
(x)
- The natural logarithm of x.
-
-
- e
(x)
- The exponential function of raising e to the value x.
-
-
- j
(n, x)
- The Bessel function of integer order n of x.
ENVIRONMENT
The following environment variables are processed by
bc:
-
-
POSIXLY_CORRECT
- This is the same as the -s option.
-
-
BC_ENV_ARGS
- This is another mechanism to get arguments to
bc. The format is the same as the command line
arguments. These arguments are processed first, so any files listed in the
environment arguments are processed before any command line argument
files. This allows the user to set up "standard" options and
files to be processed at every invocation of bc. The
files in the environment variables would typically contain function
definitions for functions the user wants defined every time
bc is run.
-
-
BC_LINE_LENGTH
- This should be an integer specifying the number of
characters in an output line for numbers. This includes the backslash and
newline characters for long numbers.
EXAMPLES
In
/bin/sh, the following will assign the value of
pi to the shell variable
pi.
pi=$(echo "scale=10; 4*a(1)" | bc -l)
The following is the definition of the exponential function used in the math
library. This function is written in POSIX
bc.
scale = 20
/* Uses the fact that e^x = (e^(x/2))^2
When x is small enough, we use the series:
e^x = 1 + x + x^2/2! + x^3/3! + ...
*/
define e(x) {
auto a, d, e, f, i, m, v, z
/* Check the sign of x. */
if (x<0) {
m = 1
x = -x
}
/* Precondition x. */
z = scale;
scale = 4 + z + .44*x;
while (x > 1) {
f += 1;
x /= 2;
}
/* Initialize the variables. */
v = 1+x
a = x
d = 1
for (i=2; 1; i++) {
e = (a *= x) / (d *= i)
if (e == 0) {
if (f>0) while (f--) v = v*v;
scale = z
if (m) return (1/v);
return (v/1);
}
v += e
}
}
The following is code that uses the extended features of
bc to
implement a simple program for calculating checkbook balances. This program is
best kept in a file so that it can be used many times without having to retype
it at every use.
scale=2
print "\nCheck book program!\n"
print " Remember, deposits are negative transactions.\n"
print " Exit by a 0 transaction.\n\n"
print "Initial balance? "; bal = read()
bal /= 1
print "\n"
while (1) {
"current balance = "; bal
"transaction? "; trans = read()
if (trans == 0) break;
bal -= trans
bal /= 1
}
quit
The following is the definition of the recursive factorial function.
define f (x) {
if (x <= 1) return (1);
return (f(x-1) * x);
}
EDITLINE OPTIONS
bc is compiled using the
editline(3) library. This
allows the user to do editing of lines before sending them to
bc. It also allows for a history of previous lines typed.
This adds to
bc one more special variable. This special
variable,
history is the number of lines of history
retained. The default value of -1 means that an unlimited number of history
lines are retained. Setting the value of
history to a
positive number restricts the number of history lines to the number given. The
value of 0 disables the history feature. For more information, read the user
manual for the
editline(3)
library.
DIFFERENCES
This version of
bc was implemented from the POSIX P1003.2/D11
draft and contains several differences and extensions relative to the draft
and traditional implementations. It is not implemented in the traditional way
using
dc(1). This version is a
single process which parses and runs a byte code translation of the program.
There is an "undocumented" option (
-c) that causes
the program to output the byte code to the standard output instead of running
it. It was mainly used for debugging the parser and preparing the math
library.
A major source of differences is extensions, where a feature is extended to add
more functionality and additions, where new features are added. The following
is the list of differences and extensions.
-
-
LANG
environment
- This version does not conform to the POSIX standard in the
processing of the
LANG
environment variable and
all environment variables starting with LC_
.
-
-
- names
- Traditional and POSIX bc have single
letter names for functions, variables and arrays. They have been extended
to be multi-character names that start with a letter and may contain
letters, numbers and the underscore character.
-
-
- strings
- Strings are not allowed to contain NUL characters. POSIX
says all characters must be included in strings. last
POSIX bc does not have a last
variable. Some implementations of bc use the period (.)
in a similar way.
-
-
- comparisons
- POSIX bc allows comparisons only in the
if statement, the while statement, and
the second expression of the for statement. Also, only
one relational operation is allowed in each of those statements.
-
-
- if
statement, else
clause
- POSIX bc does not have an
else clause.
-
-
- for
statement
- POSIX bc requires all expressions to be
present in the for statement.
-
-
- &&, ||, !
- POSIX bc does not have the logical
operators.
-
-
- read
function
- POSIX bc does not have a
read function.
-
-
- print
statement
- POSIX bc does not have a
print statement .
-
-
- continue
statement
- POSIX bc does not have a
continue statement.
-
-
- return
statement
- POSIX bc requires parentheses around the
return expression.
-
-
- array parameters
- POSIX bc does not (currently) support
array parameters in full. The POSIX grammar allows for arrays in function
definitions, but does not provide a method to specify an array as an
actual parameter. (This is most likely an oversight in the grammar.)
Traditional implementations of bc have only
call-by-value array parameters.
-
-
- function format
- POSIX bc requires the opening brace on
the same line as the define key word and the
auto statement on the next line.
-
-
- =+, =-, =*, =/, =%, =^
- POSIX bc does not require these "old
style" assignment operators to be defined. This version may allow
these "old style" assignments. Use the limits
statement to see if the installed version supports them. If it does
support the "old style" assignment operators, the statement
“a =- 1” will decrement a by 1 instead
of setting a to the value -1.
-
-
- spaces in numbers
- Other implementations of bc allow spaces
in numbers. For example, “x=1 3” would assign the value 13 to
the variable x. The same statement would cause a
syntax error in this version of bc.
-
-
- errors and execution
- This implementation varies from other implementations in
terms of what code will be executed when syntax and other errors are found
in the program. If a syntax error is found in a function definition, error
recovery tries to find the beginning of a statement and continue to parse
the function. Once a syntax error is found in the function, the function
will not be callable and becomes undefined. Syntax errors in the
interactive execution code will invalidate the current execution block.
The execution block is terminated by an end of line that appears after a
complete sequence of statements. For example,
has two execution blocks and
has one execution block. Any runtime error will terminate the execution of
the current execution block. A runtime warning will not terminate the
current execution block.
-
-
- interrupts
- During an interactive session, the
SIGINT
signal (usually generated by the control-C
character from the terminal) will cause execution of the current execution
block to be interrupted. It will display a "runtime" error
indicating which function was interrupted. After all runtime structures
have been cleaned up, a message will be printed to notify the user that
bc is ready for more input. All previously defined
functions remain defined and the value of all non-auto variables are the
value at the point of interruption. All auto variables and function
parameters are removed during the clean up process. During a
non-interactive session, the SIGINT
signal will
terminate the entire run of bc.
LIMITS
The following are the limits currently in place for this
bc
processor. Some of them may have been changed by an installation. Use the
limits statement to see the actual values.
-
-
BC_BASE_MAX
- The maximum output base is currently set at 999. The
maximum input base is 16.
-
-
BC_DIM_MAX
- This is currently an arbitrary limit of 65535 as
distributed. Your installation may be different.
-
-
BC_SCALE_MAX
- The number of digits after the decimal point is limited to
INT_MAX
digits. Also, the number of digits before
the decimal point is limited to INT_MAX
digits.
-
-
BC_STRING_MAX
- The limit on the number of characters in a string is
INT_MAX
characters.
-
-
- exponent
- The value of the exponent in the raise operation (^) is
limited to
LONG_MAX
.
-
-
- variable names
- The current limit on the number of unique names is 32767
for each of simple variables, arrays and functions.
DIAGNOSTICS
If any file on the command line can not be opened,
bc will
report that the file is unavailable and terminate. Also, there are compile and
run time diagnostics that should be self-explanatory.
HISTORY
This man page documents bc version nb1.0.
AUTHORS
Philip A. Nelson
<
phil@NetBSD.org>
ACKNOWLEDGEMENTS
The author would like to thank Steve Sommars for his extensive help in testing
the implementation. Many great suggestions were given. This is a much better
product due to his involvement.
BUGS
Error recovery is not very good yet.