The second project involves modifying the syntactic analyzer for the attached compiler by
adding to the existing grammar. The full grammar of the language is shown below. The
highlighted portions of the grammar show what you must either modify or add to the existing
grammar.
function:
function_header {variable} body
function_header:
FUNCTION IDENTIFIER [parameters] RETURNS type ;
variable:
IDENTIFIER : type IS statement
parameters:
parameter {, parameter}
parameter:
IDENTIFIER : type
type:
INTEGER | REAL | BOOLEAN
body:
BEGIN statement END ;
statement:
expression ; |
REDUCE operator {statement} ENDREDUCE ; |
IF expression THEN statement ELSE statement ENDIF ; |
CASE expression IS {case} OTHERS ARROW statement ; ENDCASE ;
operator:
ADDOP | MULOP
case:
WHEN INT_LITERAL ARROW statement
expression:
( expression ) |
expression binary_operator expression |
NOT expression |
INT_LITERAL | REAL_LITERAL | BOOL_LITERAL |
IDENTIFIER
binary_operator: ADDOP | MULOP | REMOP | EXPOP | RELOP | ANDOP | OROP
In the above grammar, the red symbols are nonterminals, the blue symbols are terminals and the
black punctuation are EBNF metasymbols. The braces denote repetition 0 or more times and the
brackets denote optional.
You must rewrite the grammar to eliminate the EBNF brace and bracket metasymbols and to
incorporate the significance of parentheses, operator precedence and associativity for all
operators. Among arithmetic operators the exponentiation operator has highest precedence
following by the multiplying operators and then the adding operators. All relational operators
have the same precedence. Among the binary logical operators, and has higher precedence than
or. Of the categories of operators, the unary logical operator has highest precedence, the
arithmetic operators have next highest precedence, followed by the relational operators and
finally the binary logical operators. All operators except the exponentiation operator are left
associative. The directives to specify precedence and associativity, such as %prec and %left,
may not be used
Your parser should be able to correctly parse any syntactically correct program without any
problem.
You must modify the syntactic analyzer to detect and recover from additional syntax errors using
the semicolon as the synchronization token. To accomplish detecting additional errors an error
production must be added to the function header and another to the variable declaration.
Your bison input file should not produce any shift/reduce or reduce/reduce errors. Eliminating
them can be difficult so the best strategy is not introduce any. That is best achieved by making
small incremental additions to the grammar and ensuring that no addition introduces any such
errors.
An example of compilation listing output containing syntax errors is shown below:
1 — Multiple errors
2
3 function main a integer returns real;
Syntax Error, Unexpected INTEGER, expecting ‘:’
4 b: integer is * 2;
Syntax Error, Unexpected MULOP
5 c: real is 6.0;
6 begin
7 if a > c then
8 b 3.0;
Syntax Error, Unexpected REAL_LITERAL, expecting ‘;’
9 else
10 b = 4.;
11 endif;
12 ;
Syntax Error, Unexpected ‘;’, expecting END
Lexical Errors 0
Syntax Errors 4
Semantic Errors 0
You are to submit two files.
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