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<head>
<title>bc(1) - Plan 9 from User Space</title>
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<tr><td width=20><td>
<tr><td width=20><td><b>BC(1)</b><td align=right><b>BC(1)</b>
<tr><td width=20><td colspan=2>
<br>
<p><font size=+1><b>NAME </b></font><br>
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bc – arbitrary-precision arithmetic language<br>
</table>
<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>bc</font></tt> [ <tt><font size=+1>−c</font></tt> ] [ <tt><font size=+1>−l</font></tt> ] [ <tt><font size=+1>−s</font></tt> ] [ <i>file ...</i> ]<br>
</table>
<p><font size=+1><b>DESCRIPTION </b></font><br>
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<i>Bc</i> is an interactive processor for a language that resembles C
but provides arithmetic on numbers of arbitrary length with up
to 100 digits right of the decimal point. It takes input from
any files given, then reads the standard input. The <tt><font size=+1>−l</font></tt> argument
stands for the name of an arbitrary precision math library. The
<tt><font size=+1>−s
</font></tt>argument suppresses the automatic display of calculation results;
all output is via the <tt><font size=+1>print</font></tt> command.
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The following syntax for <i>bc</i> programs is like that of C; <i>L</i> means
letter <tt><font size=+1>a</font></tt>-<tt><font size=+1>z</font></tt>, <i>E</i> means expression, <i>S</i> means statement.<br>
Lexical<br>
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comments are enclosed in <tt><font size=+1>/* */<br>
</font></tt>newlines end statements<br>
</table>
</table>
Names<br>
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simple variables: <i>L<br>
</i>array elements: <i>L</i><tt><font size=+1>[</font></tt><i>E</i><tt><font size=+1>]<br>
</font></tt>The words <tt><font size=+1>ibase</font></tt>, <tt><font size=+1>obase</font></tt>, and <tt><font size=+1>scale<br>
</font></tt>
</table>
</table>
Other operands<br>
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arbitrarily long numbers with optional sign and decimal point.<br>
<tt><font size=+1>(</font></tt><i>E</i><tt><font size=+1>)<br>
sqrt(</font></tt><i>E</i><tt><font size=+1>)<br>
length(</font></tt><i>E</i><tt><font size=+1>)<br>
</font></tt>number of significant decimal digits<br>
<tt><font size=+1>scale(</font></tt><i>E</i><tt><font size=+1>)<br>
</font></tt>number of digits right of decimal point<br>
<i>L</i><tt><font size=+1>(</font></tt><i>E</i><tt><font size=+1>,</font></tt><i>...</i><tt><font size=+1>,</font></tt><i>E</i><tt><font size=+1>)<br>
</font></tt>function call<br>
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</table>
Operators<br>
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<tt><font size=+1>+ − * / % ^ </font></tt> (<tt><font size=+1>%</font></tt> is remainder; <tt><font size=+1>^</font></tt> is power)<br>
<tt><font size=+1>++ −− <br>
== <= >= != < ><br>
= += −= *= /= %= ^=<br>
</font></tt>
</table>
</table>
Statements<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>E<br>
</i><tt><font size=+1>{</font></tt> <i>S</i> <tt><font size=+1>;</font></tt> ... <tt><font size=+1>;</font></tt> <i>S</i> <tt><font size=+1>}<br>
print</font></tt> <i>E<br>
</i><tt><font size=+1>if (</font></tt> <i>E</i> <tt><font size=+1>)</font></tt> <i>S<br>
</i><tt><font size=+1>while (</font></tt> <i>E</i> <tt><font size=+1>)</font></tt> <i>S<br>
</i><tt><font size=+1>for (</font></tt> <i>E</i> <tt><font size=+1>;</font></tt> <i>E</i> <tt><font size=+1>;</font></tt> <i>E</i> <tt><font size=+1>)</font></tt> <i>S<br>
</i>null statement<br>
<tt><font size=+1>break<br>
quit<br>
"</font></tt>text<tt><font size=+1>"<br>
</font></tt>
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</table>
Function definitions<br>
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<tt><font size=+1>define</font></tt> <i>L</i> <tt><font size=+1>(</font></tt> <i>L</i> <tt><font size=+1>,</font></tt> ... <tt><font size=+1>,</font></tt> <i>L</i> <tt><font size=+1>){<br>
auto</font></tt> <i>L</i> <tt><font size=+1>,</font></tt> ... <tt><font size=+1>,</font></tt> <i>L<br>
S</i> <tt><font size=+1>;</font></tt> ... <tt><font size=+1>;</font></tt> <i>S<br>
</i><tt><font size=+1>return</font></tt> <i>E
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</i>
<tt><font size=+1>}<br>
</font></tt>
</table>
</table>
Functions in<tt><font size=+1> −l</font></tt> math library<br>
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<tt><font size=+1>s(</font></tt><i>x</i><tt><font size=+1>)</font></tt>sine<br>
<tt><font size=+1>c(</font></tt><i>x</i><tt><font size=+1>)</font></tt>cosine<br>
<tt><font size=+1>e(</font></tt><i>x</i><tt><font size=+1>)</font></tt>exponential<br>
<tt><font size=+1>l(</font></tt><i>x</i><tt><font size=+1>)</font></tt>log<br>
<tt><font size=+1>a(</font></tt><i>x</i><tt><font size=+1>)</font></tt>arctangent<br>
<tt><font size=+1>j(</font></tt><i>n, x</i><tt><font size=+1>)<br>
</font></tt>Bessel function<br>
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All function arguments are passed by value.
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The value of an expression at the top level is printed unless
the main operator is an assignment or the <tt><font size=+1>−s</font></tt> command line argument
is given. Text in quotes, which may include newlines, is always
printed. Either semicolons or newlines may separate statements.
Assignment to <tt><font size=+1>scale</font></tt> influences the number of digits to
be retained on arithmetic operations in the manner of <a href="../man1/dc.html"><i>dc</i>(1)</a>. Assignments
to <tt><font size=+1>ibase</font></tt> or <tt><font size=+1>obase</font></tt> 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.
Automatic variables are pushed down during function calls. In
a declaration of an array as a function argument or automatic
variable empty square brackets must follow the array name.
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<i>Bc</i> is actually a preprocessor for <a href="../man1/dc.html"><i>dc</i>(1)</a>, which it invokes automatically,
unless the <tt><font size=+1>−c</font></tt> (compile only) option is present. In this case the
<i>dc</i> input is sent to the standard output instead.<br>
</table>
<p><font size=+1><b>EXAMPLE </b></font><br>
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Define a function to compute an approximate value of the exponential.
Use it to print 10 values. (The exponential function in the library
gives better answers.)
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<tt><font size=+1>scale = 20<br>
define e(x) {<br>
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auto a, b, c, i, s<br>
a = 1<br>
b = 1<br>
s = 1<br>
for(i=1; 1; i++) {<br>
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a *= x<br>
b *= i<br>
c = a/b<br>
if(c == 0) return s<br>
s += c<br>
</table>
}<br>
</table>
}<br>
for(i=1; i<=10; i++) print e(i)<br>
</font></tt>
</table>
<p><font size=+1><b>FILES </b></font><br>
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<tt><font size=+1>/usr/local/plan9/lib/bclib</font></tt> mathematical library<br>
</table>
<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/cmd/bc.y<br>
</font></tt>
</table>
<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man1/dc.html"><i>dc</i>(1)</a>, <a href="../man1/hoc.html"><i>hoc</i>(1)</a><br>
</table>
<p><font size=+1><b>BUGS </b></font><br>
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No <tt><font size=+1>&&</font></tt>, <tt><font size=+1>||</font></tt>, or <tt><font size=+1>!</font></tt> operators.
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A <tt><font size=+1>for</font></tt> statement must have all three <tt><font size=+1>E</font></tt>s.
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A <tt><font size=+1>quit</font></tt> is interpreted when read, not when executed.<br>
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</table>
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