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**NAME**

bc - arbitrary-precision arithmetic language

**SYNOPSIS**

bc[-c] [-l] [-s] [file...]

**DESCRIPTION**

Bcis 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-largument stands for the name of an arbitrary precision math library. The-sargument suppresses the automatic display of calculation results; all output is via thebcprograms is like that of C;Lmeans lettera-z,Emeans expression,Smeans statement. Lexical comments are enclosed in/**/newlines end statements Names simple variables:Larray elements:L[E]The wordsibase,obase, andscaleOther operands arbitrarily long numbers with optional sign and decimal point.(E)sqrt(E)length(E)number of significant decimal digitsscale(E)number of digits right of decimal pointL(E,...,E)function call Operators+-*/%^(%is remainder;^is power)++--==<=>=!=<>=+=-=*=/=%=^=StatementsE{S;...;S}Eif(E)Swhile(E)Sfor(E;E;E)Snull statementbreakquit"text" Function definitionsdefineL(L,...,L){autoL,...,LS;...;SreturnE}Functions in-lmath librarys(x)sinec(x)cosinee(x)exponentiall(x)loga(x)arctangentj(n,x)Bessel function All function arguments are passed by value. The value of an expression at the top level is printed unless the main operator is an assignment or the-scommand line argument is given. Text in quotes, which may include newlines, is always printed. Either semicolons or newlines may separate statements. Assignment toscaleinfluences the number of digits to be retained on arithmetic operations in the manner ofdc(1). Assignments toibaseorobaseset the input and output number radix respectively. 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.Bcis actually a preprocessor fordc(1), which it invokes automatically, unless the-c(compile only) option is present. In this case thedcinput is sent to the standard output instead.

**EXAMPLE**

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.) scale = 20 define e(x) { auto a, b, c, i, s a = 1 b = 1 s = 1 for(i=1; 1; i++) { a *= x b *= i c = a/b if(c == 0) return s s += c } } for(i=1; i<=10; i++) print e(i)

**FILES**

/lib/bclibmathematical library

**SOURCE**

/src/cmd/bc.y

**SEE** **ALSO**

dc(1),hoc(1)

**BUGS**

No or operators. A statement must have all three A is interpreted when read, not when executed. BC(1plan9)