bc(1) [plan9 man page]
BC(1) General Commands Manual BC(1) NAME
bc - arbitrary-precision arithmetic language SYNOPSIS
bc [ -c ] [ -l ] [ file ... ] DESCRIPTION
Bc 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 -l argument stands for the name of an arbitrary precision math library. The following syntax for bc programs is like that of C; L means letter a-z, E means expression, S means statement. Lexical comments are enclosed in /* */ newlines end statements 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) function call Operators + - * / % ^ (% is remainder; ^ is power) ++ -- == <= >= != < > = += -= *= /= %= ^= Statements E { S ; ... ; S } print E if ( E ) S while ( E ) S for ( E ; E ; E ) S null statement break quit "text" 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 an expression at the top level is printed unless the main operator is an assignment. Text in quotes, which may include new- lines, is also printed. Either semicolons or newlines may separate statements. Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc(1). Assignments 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 variable simultaneously. All variables are global to the program. Auto- matic 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. Bc is actually a preprocessor for dc(1), which it invokes automatically, unless the -c (compile only) option is present. In this case the dc input 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
/sys/lib/bclib mathematical library SOURCE
/sys/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(1)
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bc(1) General Commands Manual bc(1) Name bc - interactive arithmetic language processor Syntax bc [-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 syn- tax 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 digits to be retained on arithmetic operations in the manner of Assign- ments to ibase or obase set 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. `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 exponential function of the first ten integers: for(i=1; i<=10; i++) e(i) The command is actually a preprocessor for which it invokes automatically, 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 Also dc(1) ``BC - An arbitrary precision desk-calculator language'' ULTRIX Supplementary Documents Vol. 1: General User bc(1)