10564b1175
groff 1.23.0 added .MR to its -man macro package. The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020." From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.
Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.
Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized. groff's .MR does not. This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.
293 lines
3.7 KiB
Groff
293 lines
3.7 KiB
Groff
.TH BC 1
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.SH NAME
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bc \- arbitrary-precision arithmetic language
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.SH SYNOPSIS
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.B bc
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[
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.B -c
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]
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[
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.B -l
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]
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[
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.B -s
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]
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[
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.I file ...
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]
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.SH DESCRIPTION
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.I Bc
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is an interactive processor for a language that resembles
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C but provides arithmetic on numbers of arbitrary length with up
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to 100 digits right of the decimal point.
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It takes input from any files given, then reads
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the standard input.
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The
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.B -l
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argument stands for the name
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of an arbitrary precision math library.
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The
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.B -s
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argument suppresses the automatic display
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of calculation results; all output is via the
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.B print
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command.
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.PP
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The following syntax for
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.I bc
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programs is like that of C;
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.I L
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means letter
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.BR a - z ,
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.I E
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means expression,
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.I S
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means statement.
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.TF length(E)
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.TP
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Lexical
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.RS
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.HP
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comments are enclosed in
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.B /* */
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.HP
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newlines end statements
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.RE
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.TP
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Names
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.IP
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simple variables:
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.I L
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.br
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array elements:
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.IB L [ E ]
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.br
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The words
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.BR ibase ,
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.BR obase ,
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and
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.B scale
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.TP
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Other operands
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.IP
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arbitrarily long numbers with optional sign and decimal point.
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.RS
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.TP
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.BI ( E )
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.TP
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.BI sqrt( E )
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.TP
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.BI length( E )
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number of significant decimal digits
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.TP
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.BI scale( E )
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number of digits right of decimal point
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.TP
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.IB L ( E , ... ,\fIE\fP)
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function call
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.RE
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.TP
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Operators
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.RS
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.HP
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.B "+ - * / % ^\ "
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.RB ( %
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is remainder;
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.B ^
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is power)
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.HP
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.B "++ --\ "
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.TP
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.B "== <= >= != < >"
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.TP
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.B "= += -= *= /= %= ^="
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.RE
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.TP
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Statements
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.RS
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.br
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.I E
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.br
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.B {
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.I S
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.B ;
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\&...
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.B ;
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.I S
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.B }
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.br
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.B "print"
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.I E
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.br
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.B "if ("
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.I E
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.B )
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.I S
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.br
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.B "while ("
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.I E
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.B )
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.I S
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.br
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.B "for ("
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.I E
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.B ;
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.I E
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.B ;
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.I E
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.B ")"
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.I S
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.br
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null statement
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.br
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.B break
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.br
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.B quit
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.br
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\fL"\fRtext\fL"\fR
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.RE
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.TP
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Function definitions
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.RS
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.br
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.B define
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.I L
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.B (
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.I L
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.B ,
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\&...
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.B ,
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.I L
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.B ){
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.PD0
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.br
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.B auto
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.I L
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.B ,
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\&...
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.B ,
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.I L
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.br
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.I S
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.B ;
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\&...
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.B ;
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.I S
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.br
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.B return
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.I E
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.LP
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.B }
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.RE
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.TP
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Functions in
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.B -l
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math library
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.RS
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.TP
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.BI s( x )
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sine
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.TP
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.BI c( x )
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cosine
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.TP
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.BI e( x )
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exponential
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.TP
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.BI l( x )
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log
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.TP
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.BI a( x )
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arctangent
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.TP
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.BI j( "n, x" )
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Bessel function
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.RE
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.PP
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.DT
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All function arguments are passed by value.
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.PD
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.PP
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The value of an expression at the top level is printed
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unless the main operator is an assignment or the
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.B -s
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command line argument is given.
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Text in quotes, which may include newlines, is always printed.
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Either semicolons or newlines may separate statements.
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Assignment to
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.B scale
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influences the number of digits to be retained on arithmetic
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operations in the manner of
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.MR dc 1 .
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Assignments to
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.B ibase
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or
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.B obase
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set the input and output number radix respectively.
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.PP
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The same letter may be used as an array, a function,
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and a simple variable simultaneously.
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All variables are global to the program.
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Automatic variables are pushed down during function calls.
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In a declaration of an array as a function argument
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or automatic variable
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empty square brackets must follow the array name.
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.PP
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.I Bc
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is actually a preprocessor for
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.MR dc 1 ,
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which it invokes automatically, unless the
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.B -c
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(compile only)
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option is present.
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In this case the
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.I dc
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input is sent to the standard output instead.
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.SH EXAMPLE
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Define a function to compute an approximate value of
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the exponential.
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Use it to print 10 values.
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(The exponential function in the library gives better answers.)
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.PP
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.EX
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scale = 20
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define e(x) {
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auto a, b, c, i, s
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a = 1
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b = 1
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s = 1
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for(i=1; 1; i++) {
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a *= x
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b *= i
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c = a/b
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if(c == 0) return s
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s += c
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}
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}
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for(i=1; i<=10; i++) print e(i)
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.EE
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.SH FILES
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.B \*9/lib/bclib
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mathematical library
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.SH SOURCE
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.B \*9/src/cmd/bc.y
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.SH "SEE ALSO"
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.IR dc (1),
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.MR hoc 1
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.SH BUGS
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No
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.LR && ,
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.LR || ,
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or
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.L !
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operators.
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.PP
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A
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.L for
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statement must have all three
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.LR E s.
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.PP
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A
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.L quit
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is interpreted when read, not when executed.
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