BC(1) (User Environment Utilities) BC(1)
NAME
bc - arbitrary-precision arithmetic language
SYNOPSIS
bc [ -c ] [ -l ] [ file ... ]
DESCRIPTION
bc is an interactive processor for a language that resembles
C but provides unlimited precision arithmetic. It takes
input from any files given, then reads the standard input.
The bc(1) utility is actually a preprocessor for dc(1),
which it invokes automatically unless the -c option is
present. In this case the dc input is sent to the standard
output instead. The options are as follows:
-c Compile only. The output is sent to the standard
output.
-l Argument stands for the name of an arbitrary precision
math library.
The syntax for bc programs is as follows; L means letter
a-z, E means expression, S means statement.
Comments
are enclosed in /* and */.
Names
simple variables: L
array elements: L [ E ]
The words ``ibase'', ``obase'', and ``scale''
Other operands
arbitrarily long numbers with optional sign and
decimal point.
( E )
sqrt ( E )
length ( E ) number of significant decimal digits
scale ( E ) number of digits right of decimal point
L ( E , ... , E )
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Operators
+ - * / % ^ (% is remainder; ^ is power)
++ -- (prefix and postfix; apply to names)
== <= >= != < >
= =+ =- =* =/ =% =^
Statements
E
{ S ; ... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit
Function definitions
define L ( L ,..., L ) {
auto L, ... , L
S; ... S
return ( E )
}
Functions in -l math library
s(x) sine
c(x) cosine
e(x) exponential
l(x) log
a(x) arctangent
j(n,x) Bessel function
All function arguments are passed by value.
The value of a statement that is an expression is printed
unless the main operator is an assignment. Either
semicolons or new-lines may separate statements. Assignment
to scale influences the number of digits to be retained on
arithmetic operations in the manner of dc(1). Assignments
to ibase or obase set the input and output number radix
respectively.
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The same letter may be used as an array, a function, and a
simple variable simultaneously. All variables are global to
the program. ``Auto'' variables are pushed down during
function calls. When using arrays as function arguments or
defining them as automatic variables, empty square brackets
must follow the array name.
EXAMPLE
scale = 20
define e(x){
auto a, b, c, i, s
a = 1
b = 1
s = 1
for(i=1; 1==1; i++){
a = a*x
b = b*i
c = a/b
if(c == 0) return(s)
s = s+c
}
}
defines a function to compute an approximate value of the
exponential function and
for(i=1; i<=10; i++) e(i)
prints approximate values of the exponential function of the
first ten integers.
FILES
/usr/lib/lib.b mathematical library
/usr/bin/dc desk calculator proper
SEE ALSO
dc(1).
BUGS
The bc command does not yet recognize the logical operators,
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&& and ||.
For statement must have all three expressions (E's).
Quit is interpreted when read, not when executed.
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