Command-Line Calculator – How to Keep Fractional Values Using BC

If you are talking about calc from the apcalc package the constant Pi is defined like this:

pi() 

note, the parentheses are used even though the function does not take any arguments.

not too clear for the GUI desktop calculator,gcalctool, either, which is: Ctrl+P

Bash Arithmetic

Another possible solution is to add a simple function for Bash's builtin arithmetic. Put this in your .bashrc file to try:

=() {
    echo "$(($@))"
}

So now, you don't even need $((...)) anymore, just = which seems natural enough.

Replacement

Another thing if you want to be even faster: you can make it replace p with + and x with *. This will work for that:

=() {
    local IFS=' '
    local calc="${*//p/+}"
    calc="${calc//x/*}"
    echo "$(($calc))"
}

= 5 x 5  # Returns 25
= 50p25  # Returns 75

Now you don't even need Shift anymore, the only thing is =  in front of arithmetic.

Hexadecimal output

Output can be displayed in both decimal and hexadecimal, if so desired. (Note: using x substitution will conflict with the 0x... hex syntax)

=() {
    local answer="$(($@))"
    printf '%d (%#x)\n' "$answer" "$answer"
}

Example:

$ = 16 + 0x10
272 (0x110)

$ = 16**3 + 16**4
69632 (0x11000)

Using bc

If you want slightly more advanced calculations, you can pipe it to bc like so:

=() {
    local IFS=' '
    local calc="${*//p/+}"
    calc="${calc//x/*}"
    bc -l <<<"scale=10;$calc"
}

= 'sqrt(2)' # Returns 1.4142135623
= '4*a(1)'  # Returns pi (3.1415926532)

The functions provided by bc are as follows (and can be found from man bc):

sqrt ( expression )
       The value of the sqrt function is the square root of the expression.  
       If the expression is negative, a run time error is generated.

s (x)  The sine of x, x is in radians.

c (x)  The cosine of x, x is in radians.

a (x)  The arctangent of x, arctangent returns radians.

l (x)  The natural logarithm of x.

e (x)  The exponential function of raising e to the value x.

j (n,x)
       The Bessel function of integer order n of x.

It also supports if, for, while and variables like a programming language though if it may be better to write to a file if you wanted that.

Keep in mind that it will substitute p and x in function/variable names. It may be better to just remove the replacements.

Using gcalccmd

You can also make the function call gcalccmd (from gnome-calculator) like so:

=() {
    local IFS=' '
    local calc="$*"
    # Uncomment the below for (p → +) and (x → *)
    #calc="${calc//p/+}"
    #calc="${calc//x/*}"
    printf '%s\n quit' "$calc" | gcalccmd | sed 's:^> ::g'
}

= 'sqrt(2)' # Returns 1.4142135623
= '4^4'     # Returns 256

The available functions seem to be (taken straight from the source code), == denotes equivalent functions:

ln()
sqrt()
abs()
int()
frac()
sin()
cos()
tan()
sin⁻¹() == asin()
cos⁻¹() == acos()
tan⁻¹() == atan()
sinh()
cosh()
tanh()
sinh⁻¹() == asinh()
cosh⁻¹() == acosh()
tanh⁻¹() == atanh()
ones()
twos()