bc(1) bc(1)
NAME [Toc] [Back]
bc  arbitraryprecision arithmetic language
SYNOPSIS [Toc] [Back]
bc [c] [l] [file ...]
DESCRIPTION [Toc] [Back]
bc is an interactive processor for a language that resembles C but
provides unlimitedprecision arithmetic. It takes input from any
files given, then reads the standard input.
Options:
bc recognizes the following commandline options:
c Compile only. bc is actually a preprocessor for dc
which bc invokes automatically (see dc(1)). Specifying
c prevents invoking dc, and sends the dc input to
standard output.
l causes an arbitraryprecision math library to be
predefined. As a side effect, the scale factor is set.
Program Syntax:
L a single letter in the range a through z;
E expression;
S statement;
R relational expression.
Comments:
Comments are enclosed in /* and */.
Names:
Names include:
simple variables: L
array elements: L [ E ]
The words ibase,obase, and scale
stacks: L
Other Operands [Toc] [Back]
Other operands include:
Arbitrarily long numbers with optional sign and decimal point.
( E )
sqrt ( E )
length ( E ) number of significant decimal digits
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bc(1) bc(1)
scale ( E ) number of digits right of decimal point
L ( E , ... , E )
Strings of ASCII characters enclosed in quotes (").
Arithmetic Operators:
Arithmetic operators yield an E as a result and include:
+  * / % ^ (% is remainder (not mod,
see below); ^ is power).
++  (prefix and append; apply
to names)
= += = *= /= %= ^=
Relational Operators [Toc] [Back]
Relational operators yield an R when used as E op E:
== <= >= != < >
Statements [Toc] [Back]
E
{ S ; ... ; S }
if ( R ) S
while ( R ) S
for ( E ; R ; E ) S
null statement
break
quit
Function Definitions:
define L ( L ,..., L ) {
auto L, ... , L
S; ... S
return ( E )
}
Functions in l Math Library:
Functions in the l math library include:
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. Trigonometric angles are
in radians where 2 pi radians = 360 degrees.
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bc(1) bc(1)
The value of a statement that is an expression is printed unless the
main operator is an assignment. No operators are defined for strings,
but the string is printed if it appears in a context where an
expression result would be printed. Either semicolons or newlines
can 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, again as defined by dc(1).
The same letter can be used simultaneously as an array, a function,
and a simple variable. 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.
The % operator yields the remainder at the current scale, not the
integer modulus. Thus, at scale 1, 7 % 3 is .1 (one tenth), not 1.
This is because (at scale 1) 7 / 3 is 2.3 with .1 as the remainder.
EXAMPLES [Toc] [Back]
Define a function to compute an approximate value of the exponential
function:
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
}
}
Print approximate values of the exponential function of the first ten
integers.
for(i=1; i<=10; i++) e(i)
WARNINGS [Toc] [Back]
There are currently no && (AND) or  (OR) comparisons.
The for statement must have all three expressions.
quit is interpreted when read, not when executed.
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bc(1) bc(1)
bc's parser is not robust in the face of input errors. Some simple
expression such as 2+2 helps get it back into phase.
The assignment operators: =+ = =* =/ =% and =^ are obsolete. Any
occurences of these operators cause a syntax error with the exception
of = which is interpreted as = followed by a unary minus.
Neither entire arrays nor functions can be passed as function
parameters.
FILES [Toc] [Back]
/usr/bin/dc desk calculator executable program
/usr/lib/lib.b mathematical library
SEE ALSO [Toc] [Back]
bs(1), dc(1).
bc tutorial in Number Processing Users Guide
STANDARDS CONFORMANCE [Toc] [Back]
bc: XPG4, POSIX.2
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