GATE CSE 2016 Set 1 | Question: 45

Question

The attribute of three arithmetic operators in some programming language are given below.
$$\begin{array}{|c|l|}\hline \textbf{OPERATOR}  &  \textbf{PRECEDENCE} & \textbf{ASSOCIATIVITY} & \textbf{ARITY} \\\hline  \text{$+$} & \text{High} & \text{Left} & \text{Binary} \\\hline  \text{$-$} & \text{Medium} & \text{Right} & \text{Binary} \\\hline  \text{$*$} & \text{Low} & \text{Left} & \text{Binary} \\\hline \end{array}$$
The value of the expression $2-5+1-7*3$ in this language is ________.

Comments

@monanshi

@kenzou

what is the use of last column "ARITY"..

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Here ARITY refers to number of operands that an operator can take. 

Eg: If * has an arity of BINARY then it will indicate multiplication but if * has an arity of UNARY then it will indicate dereference operator in C language.

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I think, they mean.. PARITY

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@kirtipurohit what @Shiva Sagar Rao said is correct.

Answer 1

$2 - 5 + 1 - 7 * 3$ will be evaluated according to the precedence and associativity as given in the question as follows:
$((2 - ((5 + 1) - 7)) * 3) \Rightarrow ((2 - (-1))*3) \Rightarrow  9$

Comments

Good illustration...

Answer 2

Parser will be Bottom Up parser (made according to the precedence of operators) 

Answer 3

ans will be 9

Answer 4

+ has highest precedence, so it will be evaluated first.
2 − 5 + 1 − 7 * 3 = 2 − (5 + 1) − 7 * 3 = 2 − 6 − 7 * 3
Now, − has more precedence than *, so sub will be evaluated before * and – has right associative so (6 − 7) will be evaluated first.
2 − 6 − 7 * 3 = (2 − (6 − 7)) * 3 = (2 – (−1)) * 3 = 3 * 3 = 9