A simple calculator written in C

RATIONALE:

I did this implementaion because I did not find a nice implemenation of a "full formula" calculator online: I only found simple examples that support only one operator. This implementation supports full formulas (limited only by the size of the stack and the queue).

FEATURES / KNOWN ISSUES

Accepts the following operators:

• +: sum
• -: sub
• *: multiplication
• /: division
• %: modulus
• ^: exponentiation
• (): used to change default precedence

Current implementation is a Proof of Concept, aiming at keeping the code clear. As such, it has very strong limitations:

• Only integer artihmetic supported
• Stack and Queue used are limited in capacity (hardcoded value)
• It accepts some expressions like "()1+1", whereas tools like "bc" reject those
• Error messages can be improved
• Input parser does not recognize negative numbers. However, easy workaround is to write "(0-1)" instead of "-1"
• Acually, it does not support any unary operator (-, +, ! ...). Adding support is tricky and error-prone
  • For instance, if we accept "~" as the unary minus, expressions like "~1" and "1~" would both produce "-1"
  • To avoid this more logic needs to be added, and this is beyond the scope of this project
• In order to add correct support for unary operators, a grammar definition and parser should be used (think of lex + yacc)

HOW TO USE IT:

Compile and run: ./calculator "expression".

You can use quotes if your expression contains spaces or parenthesis. Alternatively, you can avoid spaces and scape parenthesis.

EXAMPLES:

./calculator 1+1+2-3
result: 1

./calculator 16/2/2
result: 4

./calculator 16/\(2/2\)
result: 16

./calculator " 1 + 2 * (3 - 5) * 6"
result: -23

./calculator "16/(2/2)"
result: 16

/calculator "16 % 2 % 1"
result: 0

./calculator "16 % (2 % 1)"
Modulo by zero

./calculator "2^3"
result: 8

BUILDING

To import into Eclipse CDT:

• File -> New -> Project...
• Under C/C++ choose "C Project"
• Select a Project name
  • Ensure that the "Use default location" option is not selected because here you need to specify where the resources reside in the file system, in a location other than your workspace.
• Select an appropriate Toolchain such as Executable / Linux GCC.
• Include the math library for linking ("-lm")

Manual build

Compile and link using gcc, remember to link with "-lm". Makefile is left as an excercise to the reader.