Compile your lab4 parsing executable using the 'make command',
following which you can execute ./runtests.sh to run lab4 on
a collection of valid programs and a collection of broken programs.

Note that some of the valid programs use features or tokens that you
still need to implement, so won't pass testing until you've finished
those portions of the lab.  (Initially only basic_expr, just_arr,
just_expr, and just_if will pass.)


Valid programs (in directory valid)
-----------------------------------
array_recursion - definition and call for a recursive function to sum array elements
basic_exprs - declares two vars and uses :=, *, +, -
functions - simple function definition and call
io_and_if - print, read, and if statements
just_arr - single array definition
just_expr - single call to +
just_if - single if statement
just_vars - three var defs (string, real, int)

Broken programs (in directory broken)
-------------------------------------
array_recursion - missing the datatype in the array definition
basic_exprs - missing the second VAR keyword
functions - missing the parameter list in the function definition
io_and_if - has a non-identifer in READ's parameter list
just_arr - has an invalid entry in the array definition's list of values
just_expr - has an invalid entry as one of the arguments to +
just_if - has an extra argument (after the else value)
just_vars - missing the final closing ] in the last variable definition