< >

A simple command line calculator

Posted 17 years ago

How many times have you needed to calculate something, for example the value of 0x398A3BB, so you pop up windows calculator to convert it? I did lots of times. The problem is I hate to use the mouse. It takes precious deciseconds away from software development time to remove my hands from the keyboard and use the mouse. That's why I created calc.exe. Its a simple command line calculator (and its also an example of recursive decent parsing).

Download calc.exe
Download calc.c

Examples

C:>calc 5+5*5
30.000000

c:>calc 0x30
48.000000

c:>calc (123456 % 51)/12
3.000000

Steve Hanov makes a living working on Rhymebrain.com, rapt.ink, www.websequencediagrams.com, and Zwibbler.com. He lives in Waterloo, Canada.

Post comment

edit

Matt

three years ago

RE: Yolo's request in the comments. I made some small changes in S.Hanov's excellent calc.c code that may meet your needs and use is almost daily (on Windows 10). A copy of that code is at: github.com/mccright/ccalc

Thank you again, Steve Hanov!

edit

yolo

four years ago

Can somebody fix the debug output and post it somewhere?

thx

edit

Smith

five years ago

0x30 isn't "0 times 30". For that you would input 0*30.

edit

ProDigit

five years ago

you can do the same in python.

edit

Code55

twelve years ago

Any ways to remove the debug output mentionned by Kosenkov?

"Apparently you've forgotten to remove debug output:

C:>calc 10*4

parse_expr()

parse_term()

parse_factor()

parse_num_op()

parse_rest_term()

parse_factor()

parse_num_op()

parse_rest_term()

parse_rest_expr()

40.000000

edit

A Kosenkov

13 years ago

Apparently you've forgotten to remove debug output:

C:>calc 10*4

parse_expr()

parse_term()

parse_factor()

parse_num_op()

parse_rest_term()

parse_factor()

parse_num_op()

parse_rest_term()

parse_rest_expr()

40.000000

edit

Marc Lepage

14 years ago

If you install cygwin for a Unix-like environment on Windows (bash shell and all the basic tools) then you have more options. You can use the built in expr (expression) command as a simple calculator. Or write a simple script to use Google's calculator (perhaps via Lynx or curl).

edit

Mario

14 years ago

Or you could, you know use a "real operating system" and not have to re-invent UNIX poorly :D.

edit

Simon Sapin

15 years ago

The parser example is interesting, but for a command line calculator I use this: (in ~/.bashrc)

calc() {

python -c "from math import *; print $*"

}

Example:

$ calc pi - 3

0.14159265359

This, or one of the ipython shells I have lying around.

edit

smallbug 2

16 years ago

oops

it seems that the replacement i did have effect on A ^ 9 expression...

the replacement should be :

resolve_variable(val);

if ( match_char( '^' ) ){

val_t val2;

parse_num_op( &val2 );

val->d.fval = pow( val->d.fval, val2.d.fval );

parse_rest_num_op( val );

}

parse_rest_expr( val );

edit

Small bug in the code !

16 years ago

Your code does not take in count expression like :

myVariable + 1

This is due to a bug in the void parse_rest_var function !

The following code solve this problem and seems to not have boundary effect !

void parse_rest_var( val_t* val )

{

if ( match_char( '=' ) ) {

val_t vexp;

parse_expr( &vexp );

if ( vexp.type != TYPE_FLOAT ) {

printf("Error: Tried to assign non-number to %s.\n", val->d.variable );

longjmp( env, 1 );

}

printf("Assigned to %s: ", val->d.variable );

map_add( val->d.variable, vexp.d.fval );

*val = vexp;

} else {

// -----------------------replace

// parse_rest_num_op( val );

// -- by

resolve_variable(val);

parse_rest_expr( val );

// ------------------End of modif !

}

Finding awesome developers in programming interviews

In a job interview, I once asked a very experienced embedded software developer to write a program that reverses a string and prints it on the screen. He struggled with this basic task. This man was awesome. Give him a bucket of spare parts, and he could build a robot and program it to navigate around the room. He had worked on satellites that are now in actual orbit. He could have coded circles around me. But the one thing that he had never, ever needed to do was: display something on the screen.

Fighting Blog Comment Spam with Qwen3 and Ollama

"Your program is stupid. It doesn't work," my wife told me

Zero load time file formats

When your app needs to be fast, you can't afford to load things fro disk. In this toy example, an on-disk data structure helps you instantly look up lists of related words.

Game Theory, Salary Negotiation, and Programmers

When you get a new job, you can breathe a sigh of relief, but not for long. You have an offer letter in your hand, and it is easy to miss one of the most important opportunities of your life: the starting salary. Here's what to do to increase your chances.

Asana's shocking pricing practices, and how you can get away with it too

If one apple costs $1, how much would five apples cost? How about 500? If everyday life, when you buy more of something, you get more bananas for your buck. But software companies are bucking the trend.

Throw away the keys: Easy, Minimal Perfect Hashing

Perfect hashing is a technique for building a hash table with no collisions in the minimum possible space. They are a easy to build with this simple python function.

Installing the Latest Debian on an Ancient Laptop

The challenge: Install Linux on a really old laptop. The catch: It has only 32 MB of RAM, no network ports, no CD-ROM, and the floppy drive makes creaking noises. Is it possible? Yes. Is it easy? No. Is is useful? Maybe...

My thoughts on various programming languages

Some ill-informed remarks on various programming languages.

Test Driven Development without Tears

Every company that I worked for has its own method of testing, and I've gained a lot of experience in what works and what doesn't. At last, that stack of conflicting confidentiality agreements that I got as a coop student have now all expired, so I can talk about it. (I never signed them anyway.)