dc

dc is an advanced, scientific and programmable RPN desktop calculator with macro support (re)written in C++. By default, dc supports a wide range of arithmetical, trigonometrical and numerical functions. Its capabilities can be further extended by writing user-defined programs using the embedded, turing-complete, macro system.

dc reads from the standard input, but it can also work with text files using the -f flag. Futhermore, you can decide to evaluate an expression without opening the REPL by using the -e flag.

Operands are pushed onto the stack following the LIFO policy; operators, on the other hand, pop one or more values from the stack and push back the result. By default dc is very quiet, in order to inquiry the stack you need to use one of the supported options(see below).

dc can be invoked with the following command line options:

Usage of dc:
  -e string
    	Evaluate an expression
  -f string
    	Evaluate a file containing expressions
  -v	Show version information

Some of the supported features are:

• Basic arithmetical operations(+, -, *, /, ^, %);
• Scientific notation support(5e3 -> 5000);
• Trigonometrical functions(sin, cos, tan);
• Base conversion(printBin pb, printOctal po, printHex px);
• Factorial and constants(!, pi, e);
• Stack operations:
  • Print top element(p, P);
  • Clear the stack(c);
  • Remove top element(R);
  • Swap order of top two elements(r);
  • Duplicate top element(d);
  • Dump the whole stack(f);
• Registers:
  • Store top element of the stack on register X(sX or SX);
  • Load content of register X on top of the stack(lX or LX);
• Arrays:
  • Store second-to-top of main stack into array X indexed by top-of-stack(:X);
  • Pop top-of-stack and use it as an index for array X(;X);
• Macros:
  • Define a new macro inside square brackets([ ]);
  • Executing a macro from the stack(x);
  • Evaluate a macro by comparing top-of-head and second-of-head elements(>X, <X, >=X, <=X, != where X is a register).

And much more. You can find the complete manual here.

Installation

dc is written in Rust. You can compile it by issuing the following command:

$> cargo build --verbose --release

You will find the output binary at:

$> target/release/dc

To run unit tests, instead, type:

$> cargo test --all

Usage

dc can be used in three different ways:

1. From the interactive REPL(run it without any argument);
2. By evaluating an inline expression, i.e.

   $> dc -e "5 5 + p"
   

3. By evaluating a text file, i.e.

   $> cat foo
   2 4 - # Evaluate 2 - 4
   2 ^   # Evaluate x^2
   p     # Print the result(4)
   $> dc -f foo
   4
   

Below there are more examples.

1. Evaluate

\frac{-5 + \sqrt(25 - 16)}{2}

-5 25 16 - v + 2 / p

where v is the square root function

2. Evaluate

\frac{.5 + .9}{3^4}

.5 .9 + 3 4 ^ / p

3. Evaluate 10 + 5 inline(i.e. without opening the REPL):

$> dc -e "10 5 +"

4. Evaluate an expression from a file:

$> cat foo
    5 5 + 
    2 d * v 
    f
$> dc -f ./foo

5. Evaluate

\sin(2\pi) + \cos(2\pi)

2 pi * sin 2 pi * cos + p

6. Swap top two elements using registers(you can also use the r command):

5 4 p # Load some values on the stack(output: 4)
sA sB # Pop values and store them into the registers 'A' and 'B'
lA lB # Push 'A' and 'B' content onto the stack
p     # Print top element(output: 5)

7. Print out numbers from 1 through user-defined upper bound:

[ p 1 + d lN >L ] sL # Print numbers from 1 through 'N'

[ Enter limit: ] P # Ask user for limit 'N'
? 1 + sN # Read from stdin
c 1 lL x # Clear the stack, add lower bound, load and execute macro

8. Sum the first 36 natural numbers(😈), i.e.,

\sum_{i=1}^{37} i = 666

$> dc -e "36 [ d 1 - d 1 <F + ] d sF x p"

5. Prints the first 20 values of n!:

[ la 1 + d sa * p la 20 >y ] sy
0 sa 1
ly x

9. Computes the factorial of a given number:

[ ln 1 - sn ln la * sa ln 1 !=f ] sf
[ Enter value: ] P ? sn
ln sa
lf x
la p

10. Computes the Greatest Common Divisor(GCD) between two user-defined numbers A and B:

[ Enter A: ] P R ?
[ Enter B: ] P R ?
[ d Sa r La % d 0 <a ] d sa x +
[ GCD(A,B)= ] P R p

11. Computes the Least Common Multiple(LCM) between two user-defined numbers A and B:

[ Enter A: ] P R ? d sA
[ Enter B: ] P R ? d SA
[ d Sa r La % d 0 <a ] d sa x +
LA lA * r /
[ LCM(A,B)= ] P R p

12. Find the roots of a quadratic equation of the form:

ax^2 + bx + c = 0

with $$a,b,c \in \mathbb{R}, a \neq 0$$

using the formula

x_{1,2} = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

#!/usr/local/bin/dc -f
# GIVEN A QUADRATIC EQUATION OF THE FORM
# AX^2 + BX + C = 0
# COMPUTE ITS REAL ROOTS
# THIS PROGRAM DOES NOT WORK WITH CMPLX NUMBERS
# DEVELOPED BY MARCO CETICA 2023
#
[ Enter A: ] P ? sA
[ Enter B: ] P ? sB
[ Enter C: ] P ? sC
lB 2 ^ 4 lA lC * * - v sD
lB -1 * lD - lA # NEGATIVE DELTA
2 * / sS # FIRST SOLUTION
lB -1 * lD + lA # POSITIVE DELTA
2 * / SS # SECOND SOLUTION
[ X: ] P R lS p
[ Y: ] P R LS lS p

License

GPLv3