The fourth project involves modifying the semantic analyzer for the attached compiler by adding
checks for semantic errors. The static semantic rules of this language are the following:
Variables and parameter names have local scope. The scope rules require that all names be
declared and prohibit duplicate names within the same scope. The type correspondence rules are
as follows:
Boolean expressions cannot be used with arithmetic or relational operators.
Arithmetic expressions cannot be used with logical operators.
Reductions can only contain numeric types.
Only integer operands can be used with the remainder operator.
The two statements in an if statement must match in type. No coercion is performed.
All the statements in a case statement must match in type. No coercion is performed.
The type of the if expression must be Boolean.
The type of the case expression must be Integer
A narrowing variable initialization or function return occurs when a real value is being
forced into integer. Widening is permitted.
Boolean types cannot be mixed with numeric types in variable initializations or function
returns.
Type coercion from an integer to a real type is performed within arithmetic expressions.
You must make the following semantic checks. Those highlighted in yellow are already
performed by the code that you have been provided, although you are must make minor
modifications to account for the addition of real types and the need to perform type coercion and
to handle the additional arithmetic and logical operators.
Using Boolean Expressions with Arithmetic Operator
Using Boolean Expressions with Relational Operator
Using Arithmetic Expressions with Logical Operator
Reductions containing nonnumeric types
Remainder Operator Requires Integer Operands
If-Then Type Mismatch
Case Types Mismatch
If Condition Not Boolean
Case Expression Not Integer
Narrowing Variable Initialization
Variable Initialization Mismatch
Undeclared Variable
Duplicate Variable
Narrowing Function Return
This project requires modification to the bison input file, so that it defines the additional
semantic checks necessary to produce these errors and addition of functions to the library of type
checking functions already provided in types.cc. You must also make some modifications to
the functions provided. You need to add a check to the checkAssignment function for
mismatched types in the case that Boolean and numeric types are mixed. You need to also add
code to the checkArithmetic function to coerce integers to reals when the types are mixed and
the error message must be modified to indicate that numeric rather than only integer types are
permitted.
The provided code includes a template class Symbols that defines the symbol table. It already
includes a check for undeclared identifiers. You need to add a check for duplicate identifiers.
Like the lexical and syntax errors, the compiler should display the semantic errors in the
compilation listing, after the line in which they occur. An example of compilation listing output
containing semantic errors is shown below:
1 — Test of Multiple Semantic Errors
2
3 function test a: integer returns integer;
4 b: integer is
5 if a + 5 then
6 2;
7 else
8 5;
9 endif;
Semantic Error, If Expression Must Be Boolean
10 c: real is 9.8 – 2 + 8;
11 d: boolean is 7 = f;
Semantic Error, Undeclared f
12 begin
13 case b is
14 when 1 => 4.5 + c;
15 when 2 => b;
Semantic Error, Case Types Mismatch
16 others => c;
17 endcase;
18 end;
Lexical Errors 0
Syntax Errors 0
Semantic Errors 3
0 comments