====================================
CPW Pt. 9: Calculator with Variables					[TOC]
====================================

---- VIDEO ------------------------------
https://www.youtube.com/embed/X-Q12rYrg_w
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Quiz 23: Calculator with Variables
==================================
Reorganize the source files as shown in the video (create a separate header an
source file for the parser). Extend the calculator so that it supports
calculations with variables.

The grammar for the calculator should be

---- LATEX ---------------------------------------------------------------------
\begin{array}{rcl}
\text{input-sequence}
    & = &
    \{\;
    \text{expr-statement}\;
    \}\;
    \texttt{EOI}
    \\
\text{expr-statement}
    & = &
    \text{assignment-expr}\;
    \texttt{;}\;
    \\
\text{assignment-expr}
    & = &
    \text{expr}\;
    [\;
    \texttt{=}\;
    \text{assignment-expr}\;
    ]\;
    \\
\text{expr}
    & = &
    \text{term}\;
    \{\;
      (\;
      \texttt{"+"}\; |\; \texttt{"-"}\;
      )\;
      \text{term}
    \}
    \\
\text{term}
    & = &
    \text{power-expr}\;
    \{\;
      (\;
      \texttt{"*"}\; |\; \texttt{"/"}\;
      )\;
      \text{power-expr}
    \}
    \\
\text{power-expr}
    & = &
    \text{unary-expr}\;
    [\;
      \texttt{"^"}\;
      \text{power-expr}
    ]\;
    \\
\text{unary-expr}
    & = &
    \text{factor}\;
    |\;
    (\; \texttt{"+"}\; |\; \texttt{"-"}\;)\;
    \text{unary-expr}
    \\
\text{factor}
    & = &
    \text{identifier}\;
    \\
    & | &
    \text{dec-literal}\;
    \\
    & | &
    \text{hex-literal}\;
    \\
    & | &
    \text{oct-literal}\;
    \\
    & | &
    \texttt{"("}\;
    \text{assignment-expr}\;
    \texttt{")"}\;
    \\
\end{array}
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Note that for the assignment expressions actually an optional group is
sufficient!

As L-values only identifiers are allows. Undeclared identifiers are always
accepted and have value 0.

Submit your program with

---- CODE (type=txt) -----------------------------------------------------------------------------------------------------------------------
submit hpc quiz23 xtest_calc.c parser.h parser.c expr.h expr.c str.h str.c sym.h sym.c ustr.h ustr.c lexer.h lexer.c tokenkind.h tokenkind.c
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