bc(1)bc(1)Namebc - interactive arithmetic language processor
Syntaxbc [-c] [-l] [file...]
Description
The command provides an interactive processor for a language which
resembles C but provides unlimited precision arithmetic. It takes
input from any files given, then reads the standard input. The -l
argument stands for the name of an arbitrary precision math library.
The syntax for 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 )
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 dig‐
its to be retained on arithmetic operations in the manner of Assign‐
ments to ibase or obase set the input and output number radix respec‐
tively.
The same letter may be used as an array, a function, and a simple vari‐
able 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.
The following example defines 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
}
}
The following command line then prints approximate values of the expo‐
nential function of the first ten integers:
for(i=1; i<=10; i++) e(i)
The command is actually a preprocessor for which it invokes automati‐
cally, unless the -c (compile only) option is present. In this case
the input is sent to the standard output instead.
Options-c Compiles input only.
-l Names arbitrary precision math library.
Restrictions
The for statement must have all three E's.
Quit is interpreted when read, not when executed.
Variables must be a single lower case letter. Upper case letters are
used only as digits for bases greater than 10.
Files
mathematical library
See Alsodc(1)
``BC - An arbitrary precision desk-calculator language'' ULTRIX Supple‐
mentary Documents Vol. 1: General User
bc(1)
