Question

Please answer the questions below:

1. Given an example of the shortest IF statement in Modula-2. (“Shortest” means fewest
number of lexemes.)
2. State whether or not each of the following language constructs is syntactically valid.
For each invalid construct, give the number of the syntax rule that is violated.
(a) Declaration:
CONST mask = BITSET{9..11}; divisor = 512;
(b) Declaration:
PROCEDURE LessThan(addr1, addr2: ADDRESS): BOOLEAN;
VAR r1, r2: POINTER TO REAL;
BEGIN
r1 := addr1;
r2 := addr2;
RETURN r1^ < r2^
END;
(c) Statement:
LOOP
Position(pattern, source, index, found);
IF NOT found THEN EXIT END;
Delete(source, index, Length(pattern), success);
Insert(replacement, source, index, success);
IF NOT success THEN
Error("Buffer overflow in Replace");
END
END
(d) Statement:
IF queue = NIL THEN
temp^.next := temp;
temp^.previous := temp;
queue := temp
ELSE
temp^.next := queue;
temp^.previous := queue^.previous;
queue^.previous^.next := temp;
queue^.previous := temp
END

Answer 1

1.CONST mask=BISTE{9..11};divisor=512;

Rules:1.1 BISTE invalid keyword.It should not contain any special symbol or alphabate.

1.2: Varible length should be in 8 bytes .

1.3: Before declaring or initializing variable name declare datatype of varible.(int ,float,char,const..)

2. PROCEDURE LessThan(addr1, addr2: ADDRESS): BOOLEAN;

VAR r1, r2: POINTER TO REAL;

2.1: LessThan is name of procedure but (addr1,addr2:Address); not allowed

2.2: VAR not allowed

3. Improper parameters