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• bc is a command-line calculator and primitive language

• bc is a POSIX standard but the GNU version has added functionality

• bc by default runs in integer mode (scale=0) and with no trig functions, running “bc -l” loads trig functions and sets scale to 20

• bc can only take expressions on standard input (or in files), not directly on the command line e.g. echo 3+4 | bc

• This is a great collection of bc functions. funcs.bc and logic.bc are the basic ones. This is a collection of more sanely named basic scientific calculator functions.

• useful bash aliases

mbc ()
{
  echo $@ | bc -l -q ~/bin/extensions.bc
}
 
alias bc="bc -l -q ~/bin/extensions.bc"

So now “mbc '(3+5)/6'” works as expected

• bc uses readline so ⇑ and ⇓ (for history) and ctrl-r (for searching) work as expected.

• Any alphanumeric variable name is allowed once it starts with a letter.

• There are 4 special variables
  • last - The value of the last printed number
  • scale - number of decimal places to display
  • ibase - base to be used for input values
  • obase - base to be used for output values

• Any expression that is not an assignment is displayed and stored in the last variable.

• Every value and every expression is a number. The assignment operator returns 0. Booleans are 0 / 1.

• Basic + - / * = == work. % is modulo . ^ is integer exponentiation.

• Predefined functions are :
  • s - sine , c - cosine
  • a - arctan , j(n,x) - Bessel function
  • l - natural log , e - e to the power of
  • length, scale, sqrt - as named

• && , || , ! work as expected (return 0 or 1).

• New functions are easy to define e.g.

  define log(x,y) {
    auto retval = l(y)/l(x)
    return retval
  }

Note that the auto keyword is used to declare a local variable.

• if(cond) else, while(cond) and for(init;cond;inc) control flow structures are all supported. break and continue are also supported.

• read() is used to read a value from standard input. print() prints to standard output.

• Arrays can be used by using [subscript] after the array name.

• Special commands include quit, limits and warranty.