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bc |
bc [options] [files] bc is a language (and compiler) whose syntax resembles that of C, but with unlimited-precision arithmetic. bc consists of identifiers, keywords, and symbols, which are briefly described in the following entries. Examples are given at the end. Interactively perform arbitrary-precision arithmetic or convert numbers from one base to another. Input can be taken from files or read from the standard input. To exit, type quit or EOF. Options-l, --mathlib Make functions from the math library available. -s, --standard Ignore all extensions, and process exactly as in POSIX. -w, --warn When extensions to POSIX bc are used, print a warning. -q, --quiet Do not display welcome message. -v, --version Print version number. IdentifiersAn identifier is a series of one or more characters. It must begin with a lowercase letter but may also contain digits and underscores. No uppercase letters are allowed. Identifiers are used as names for variables, arrays, and functions. Variables normally store arbitrary-precision numbers. Within the same program you may name a variable, an array, and a function using the same letter. The following identifiers would not conflict: x Variable x. x i Element i of array x. i can range from 0 to 2047 and can also be an expression. x y z Call function x with parameters y and z. Input-output keywordsibase, obase, scale, and last store a value. Typing them on a line by themselves displays their current value. You can also change their values through assignment. The letters A-F are treated as digits whose values are 10-15. ibase = n Numbers that are input (e.g., typed) are read as base n (default is 10). obase = n Numbers that are displayed are in base n (default is 10). Note: Once ibase has been changed from 10, use A to restore ibase or obase to decimal. scale = n Display computations using n decimal places (default is 0, meaning that results are truncated to integers). scale is normally used only for base-10 computations. last Value of last printed number. Statement keywordsA semicolon or a newline separates one statement from another. Curly braces are needed when grouping multiple statements. if (rel-expr) [else ] Do one or more statements if relational expression rel-expr is true. Otherwise, do nothing, or if else (an extension) is specified, do alternative statements. For example: if(x==y) elsewhile (rel-expr Repeat one or more statements while rel-expr is true; for example: while(i>0)for (expr1 rel-expr expr2 Similar to while; for example, to print the first 10 multiples of 5, you could type: for(i=1; i<=10; i++) i*5GNU bf does not require three arguments to for. A missing argument 1 or 3 means that those expressions will never be evaluated. A missing argument 2 evaluates to the value 1. break Terminate a while or for statement. print list GNU extension. It provides an alternate means of output. list consists of a series of comma-separated strings and expressions; print displays these entities in the order of the list. It does not print a newline when it terminates. Expressions are evaluated, printed, and assigned to the special variable last. Strings (which may contain special characters, i.e., characters beginning with ) are simply printed. Special characters can be: a Alert or bell b Backspace f Form feed n Newline r Carriage return q Double quote t Tab Backslash continue GNU extension. When within a for statement, jump to the next iteration. halt GNU extension. Cause the bc processor to quit. limits GNU extension. Print the limits enforced by the local version of bc. Function keywordsdefine f args auto x y Set up x and y as variables local to a function definition, initialized to 0 and meaningless outside the function. Must appear first. return(expr Pass the value of expression expr back to the program. Return 0 if (expr) is left off. Used in function definitions. sqrt(expr Compute the square root of expression expr. length(expr Compute how many significant digits are in expr. scale(expr Same as length, but count only digits to the right of the decimal point. read( ) GNU extension. Read a number from standard input. Return value is the number read, converted via the value of ibase. Math library functionsThese are available when bc is invoked with -l. Library functions set scale to 20. s(angle Compute the sine of angle, a constant or expression in radians. c(angle Compute the cosine of angle, a constant or expression in radians. a(n Compute the arctangent of n, returning an angle in radians. e(expr Compute e to the power of expr. l(expr Compute the natural log of expr. j(n x Compute the Bessel function of integer order n. OperatorsThese consist of operators and other symbols. Operators can be arithmetic, unary, assignment, or relational: arithmetic unary assignment relational < <= > >= == != Other symbolsEnclose comments. Control the evaluation of expressions (change precedence). Can also be used around assignment statements to force the result to print. Use to group statements. Indicate array index. text Use as a statement to print text. ExamplesNote in these examples that when you type some quantity (a number or expression), it is evaluated and printed, but assignment statements produce no display. ibase = 8 Octal inputEvaluate this octal number Terminal displays decimal value obase = 2 Display output in base 2 instead of base 10 Octal input Terminal now displays binary value ibase = A Restore base-10 input scale = 3 Truncate results to 3 decimal places Evaluate a division Oops! Forgot to reset output base to 10 obase=10 Input is decimal now, so A isn't needed Terminal displays result (truncated) The following lines show the use of functions: define p(r,n) Value returnedscale=5 x=p(2.5,2) x = 2.5 ^ 2 x Print value of x length(x) Number of digits scale(x) Number of places right of decimal point |
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