Yacc/Lex/Readline-- Documentation

0.4

This is an example of using Yacc/Lex-- and Readline-- together to form a Command Line Interface (CLI) based toy calculator. It's written completly in C++, and all constructs are done in an Object-Oriented way.

FeaturesOverview

The calculator has the following features:

Normal arithmatic on real valued numbers, such as '+', '-', '*', and '/':

        toycalc> 2 + 3
          2 + 3  => 5
        toycalc> 3 - 1
          3 - 1  => 2
        toycalc> 3.14 * 2.17
          3.14 * 2.17  => 6.8138
        toycalc> 4 / 2
          4 / 2  => 2

Scopeing partial expressions using '(' and ')':

        toycalc> 2 + 3 * 4  
          2 + 3 * 4  => 14
        toycalc> (2 + 3) * 4
          (2 + 3) * 4  => 20

Variable declaration and assignment using '=':

        toycalc> a = 10
          a = 10  => 10
        toycalc> b = 20
          b = 20  => 20
        toycalc> a = 30
          a = 30  => 30
        toycalc> a
          a  => 30

Arithmatic on variables:

        toycalc> c = a + b
          c = a + b  => 50
        toycalc> c
          c  => 50

Definition and evaluation of user functions:

  toycalc> f(x) { x + 10 }
          f  => 0
  toycalc> f(a)           
    f(a)  => 40

Built in functions and variables:

        toycalc> list
        Functions:
                sin(x) {  ...  }
                cos(x) {  ...  }
                tan(x) {  ...  }
                asin(x) {  ...  }
                acos(x) {  ...  }
                atan(x) {  ...  }
                exp(x) {  ...  }
                log(x) {  ...  }
                f(x) { x + 10 }
        Variables:
                pi      = 3.14159
                e       = 2.71828
                a       = 30
                b       = 20
                c       = 50
        toycalc> sin(pi/2)
          sin(pi / 2)  => 1

Normal Readline editing of the command-line, such as <th> Key-sequence</th><th>Effect</th> <th> Key-sequence</th><th>Effect</th>

C-a Beginning of line C-d End of line

C-@ Mark C-w Cut

C-y Paste M-w Copy
... and loads more. All ofcourse configurable via users ~/.inputrc in the group toycalc.
History! Recall old commands by pressing C-p (Up-arrow), and C-n (Down-arrow), and all such things you would expect from a CLI.


Motivation


I'm using this project as a studie tool to get to know Yacc/Lex and Readline. My long term project is to make an interactive C++ interpretor written entirely in - you guessed it C++. Well, not entirely.

Some parts will be in Yacc/Lex, some in C. The C stuff comes in when I when to use an existing GNU library for some stuff, like Yacc and Lex, but also the Libtool API for loading shared libraries and modules at run-time is planned to be used. However, I'll try to wrap these C API's in C++ classes to make the code consistent and neat.

          
          

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            Last update Wed Feb 5 03:34:02 2003

            Christian Holm

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