Programs

A program is a sequence of statements. For example:

   int y ;
   y = 6 ;
   print y + 9 ;

A program may contain comments, which are ignored by the parser. Comments can start with the token // and extend to the end of the line. They can also start with /* and extend to the next */.

Statements

Any expression followed by a semicolon ; can be used as a statement.

    SExp.    Stm    ::= Exp ";" ;

Any declaration followed by a semicolon ; can be used as a statement. Declarations have one of the following formats:

• a type and one variable (as in function parameter lists),

        int i ;
  

• a type and many variables,

        int i, j ;
  

• a type and one initialized variable,

        int i = 6 ;
  

  Statements also include
• Statements returning an expression,

        return i + 9 ;
  

• While loops, with an expression in parentheses followed by a statement,

        while (i < 10) ++i ;
  

• Conditionals: if with an expression in parentheses followed by a statement, else, and another statement,

        if (x > 0) return x ; else return y ;
  

• Blocks: any list of statements (including the empty list) between curly brackets. For instance,

        { 
          int i = 2 ;
          {
          }
          i++ ;
        }
  

• Printing statements, to print the value of any expression. Examples:

        print 2+3 ;
        print "hello" ;
  

Expressions

Expressions are specified with the following table that gives their precedence levels. Infix operators are assumed to be left-associative, except assignments, which are right-associative. The arguments in a function call can be expressions of any level. Otherwise, the subexpressions are assumed to be one precedence level above the main expression.

Types

The available types are bool, double, int, string, and void.

Identifiers

An identifier is a letter followed by a list of letters, digits, and underscores.

To test

Your grammar must be able to parse the examples in [the example directory ./examples/].

An easy way to perform the test is to run the test file test1.sh. In a Unix shell, you can use the command source test1.sh. This assumes that

• your parser TestMini is in the same directory
• you have a copy of examples/ or a symbolic link to it in the same directory.

Running the test produces the file log.txt, which you must submit together with the file Mini.cf.

An optional extension: functions

Function definitions

A program is a sequence of definitions. You can treat this as an alternative projection to programs defined as sequences of statements.

A function definition has a type, a name, an argument list, and a body. Example:

    int foo(double x, int y)
    {
      return y + 9 ;
    }

An argument list is a comma-separated list of argument declarations. It is enclosed in parentheses ( and ).

An argument declaration has a type and an identifier, for instance

    int x

Notice that argument declarations with multiple variables (int x, y) are not included, even though a declaration that occurs as a statement (as shown above), can have multiple variables.

A function body is a list of statements enclosed in curly brackets { and } .

Function calls

A function call is an expression of level 15, of form f(exp,...,exp) where f is an identifier. The argument list exp,...,exp has zero or more comma-separated expressions of level 0.

Test criteria

Your parser must parse all additional example programs.