BC(1) BSD Reference Manual BC(1)

bc- arbitrary-precision arithmetic language and calculator

bc[-cl] [-eexpression] [file...]

bcis an interactive processor for a language which resembles C but pro- vides unlimited precision arithmetic. It takes input from any expressions on the command line and any files given, then reads the standard input. Options available:-c bcis actually a preprocessor for dc(1), which it invokes au- tomatically, unless the-c(compile only) option is present. In this case the generated dc(1) instructions are sent to the stan- dard output, instead of being interpreted by a running dc(1) pro- cess.-eexpressionEvaluateexpression. If multiple-eoptions are specified, they are processed in the order given, separated by newlines.-lAllow specification of an arbitrary precision math library. The definitions in the library are available to command line expres- sions. The syntax forbcprograms is as follows: 'L' means letter a-z; 'E' means expression; 'S' means statement. As a non-portable extension, it is pos- sible to use long names in addition to single letter names. A long name is a sequence starting with a lowercase letter followed by any number of lowercase letters and digits. The underscore character ('_') counts as a letter. Comments are enclosed in /* and */ are enclosed in # and the next newline The newline is not part of the line comment, which in itself is a non- portable extension. Names simple variables: L array elements: L [ E ] The words 'ibase', 'obase', and 'scale' The word 'last' or a single dot 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 ) The sequence '\<newline><whitespace>' is ignored within numbers. Operators The following arithmetic and logical operators can be used. The semantics of the operators is the same as in the C language. They are listed in order of decreasing precedence. Operators in the same group have the same precedence.Operator Associativity Description++ -- none increment, decrement - none unary minus ^ right power * / % left multiply, divide, modulus + - left plus, minus = += -= *= /= %= ^= right assignment == <= >= != < > none relational ! none boolean not && left boolean and || left boolean or Note the following: • The relational operators may appear in any expression. The IEEE Std 1003.2 ("POSIX.2") standard only allows them in the condi- tional expression of an 'if', 'while' or 'for' statement. • The relational operators have a lower precedence than the as- signment operators. This has the consequence that the expres- siona = b < cis interpreted as(a = b) < c, which is probably not what the programmer intended. • In contrast with the C language, the relational operators all have the same precedence, and are non-associative. The expres- siona < b < cwill produce a syntax error. • The boolean operators (!, && and ||) are non-portable exten- sions. • The boolean not (!) operator has much lower precedence than the same operator in the C language. This has the consequence that the expression!a < bis interpreted as!(a < b). Prudent pro- grammers use parentheses when writing expressions involving boolean operators. Statements E { S ; ... ; S } if ( E ) S if ( E ) S else S while ( E ) S for ( E ; E ; E ) S null statement break continue quit a string of characters, enclosed in double quotes print E ,..., E A string may contain any character, except double quote. The if statement with an else branch is a non-portable extension. All three E's in a for statement may be empty. This is a non-portable extension. The continue and print statements are also non-portable extensions. The print statement takes a list of comma-separated expressions. Each ex- pression in the list is evaluated and the computed value is printed and assigned to the variable 'last'. No trailing newline is printed. The ex- pression may also be a string enclosed in double quotes. Within these strings the following escape sequences may be used: '\a' for bell (alert), '\b' for backspace, '\f' for formfeed, '\n' for newline, '\r' for carriage return, '\t' for tab, '\q' for double quote and '\\' for backslash. Any other character following a backslash will be ignored. Strings will not be assigned to 'last'. Function definitions define L ( L ,..., L ) { auto L, ... , L S; ... S return ( E ) } As a non-portable extension, the opening brace of the define statement may appear on the next line. The return statement may also appear in the following forms: return return () return E The first two are equivalent to the statement "return 0". The last form is a non-portable extension. Not specifying a return statement is equivalent to writing "return (0)". Functions available in the math library, which is loaded by specifying the-lflag on the command line 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. The value printed is assigned to the special variable 'last'. This is a non-portable extension. A single dot may be used as a synonym for 'last'. Either semicolons or newlines may separate statements. Assignment toscaleinfluences the number of digits to be re- tained on arithmetic operations in the manner of dc(1). Assignments toibaseorobaseset the input and output number radix respectively. The same letter may be used as an array, a function, and a simple vari- able simultaneously. All 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. For example 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 } } defines a function to compute an approximate value of the exponential function and for(i=1; i<=10; i++) e(i) prints approximate values of the exponential function of the first ten integers. $ bc -l -e 'scale = 500; 2 * a(2^10000)' -e quit prints an approximation of pi.

/usr/share/misc/bc.library math library, read when the-loption is specified on the command line.

dc(1) "BC - An Arbitrary Precision Desk-Calculator Language",/usr/share/doc/usd/06.bc/.

Thebcutility is expected to conform to the IEEE Std 1003.2 ("POSIX.2") specification.

Thebcfirst command appeared in Version 6 AT&T UNIX. A complete rewrite of thebccommand first appeared in OpenBSD 3.5.

The original version of thebccommand was written by Robert Morris and Lorinda Cherry. The current version of thebcutility was written by Otto Moerbeek.

'Quit' is interpreted when read, not when executed. Some non-portable extensions, as found in the GNU version of thebcutil- ity are not implemented (yet). August 8, 1991 3

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