bc.1

UNIX版本6的源代码

.th BC I 2/20/75
.sh NAME
bc \*- arbitrary precision interactive language
.sh SYNOPSIS
.bd bc
[
.bd \-l
] [ file ... ]
.sh DESCRIPTION
.it Bc
is 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 a library of mathematical subroutines
which contains sine (named `s'), cosine (`c'),
arctangent (`a'), natural logarithm (`l'),
and exponential (`e').
The syntax for 
.it bc
programs is as follows;
E means expression, S means statement.
.s3
.lp +6 6
Comments
.br
are enclosed in /* and */.
.s3
.lp +6 6
Names
.br
letters a\-z
.br
array elements: letter[E]
.br
The words `ibase', `obase', and `scale'
.s3
.lp +6 6
Other operands
.br
arbitrarily long numbers with optional sign and decimal point.
.br
( E )
.br
sqrt ( E )
.br
<letter> ( E , ... , E )
.s3
.lp +6 6
Operators
.br
+  \-  *  /  %  ^
.br
++   \-\-         (prefix and postfix; apply to names)
.br
==  <=  >=  !=  <  >
.br
=  =+  =\-  =*  =/  =%  =^
.br
.s3
.lp +6 6
Statements
.br
E
.br
{ S ; ... ; S }
.br
if ( E ) S
.br
while ( E ) S
.br
for ( E ; E ; E ) S
.br
null statement
.br
break
.br
quit
.s3
.lp +6 6
Function definitions are exemplified by
.br
define <letter> ( <letter> ,..., <letter> ) {
.br
	auto <letter>, ... , <letter>
.br
	S; ... S
.br
	return ( E )
.br
}
.s3
.i0
.dt
All function arguments are passed by value.
.s3
The value of a statement that is an expression is printed
unless the main operator is an assignment.
Either semicolons or newlines may separate statements.
Assignment to
.it scale
influences the number of digits to be retained on arithmetic
operations.
Assignments to
.it ibase
or
.it obase
set the input and output number radix respectively.
.s3
The same letter may be used as an array name, a function name,
and a simple variable simultaneously.
`Auto' variables are saved and restored during function calls.
All other variables are global to the program.
When using arrays as function arguments
or defining them as automatic variables
empty square brackets must follow the array name.
.s3
For example
.s3
.nf
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
	}
}
.s3
.fi
defines a function to compute an approximate value of
the exponential function and
.s3
.nf
	for(i=1; i<=10; i++) e(i)
.fi
.s3
prints approximate values of the exponential function of
the first ten integers.
.sh FILES
/usr/lib/lib.b	mathematical library
.sh "SEE ALSO"
.it dc
(I),
C Reference Manual,
``BC \- An Arbitrary Precision Desk-Calculator Language.''
.sh BUGS
No &&, | | yet.
.br
.it for
statement must have all three E's
.br
.it quit
is interpreted when read, not when executed.