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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.

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