編譯原理作業1、2

Exercise 1.1

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Question 1

• In this course, we will try to develop a compiler. I find it hard to develop a compiler, for the sake of the fact that C or C++ have complicated syntax rules and character set. So an artificial computer language with a small character set and easy syntax rules occurred to me.

Question 2

• A program written in C++

int c0 = 2;
int c1 = 5;
while (c1 != 0) {
    co += 1;
    c1 -= 1;
}

• Same program written in the proposed language

+2       Cell c0 = 2
> +5     Cell c1 = 5

[        Start your loops with your cell pointer on the loop counter                (c1 in our case)
< +1      Add 1 to c0
> -1      Subtract 1 from c1
]         End your loops with the cell pointer on the loop counter

Question 3

Syntax:

Character	Meaning
program start	char array[INFINITELY_LARGE_SIZE] = {0};char *ptr=array;
>	++ptr
<	--ptr
+1	*ptr += 1
-1	*ptr -= 1
.	putchar(*ptr)
,	*ptr=getchar()
[	while (*ptr) {
]	}
0 - 9	digit

digit ::= 0 | 1 | ... | 9
symbol ::= + | -
operation ::= symbol {digit}

Semantics:

Each character in character set means one operator except digits which need to follow a symbol. The format and style is useless.

Question 4

First I need to complete the design of my language. Then I have to build the compiler of my language.

Exercise 1.2

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Question 1

（C is a machine language)
Stage 1:

Stage 2:

Exercise 2.1

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Exercise 2.2

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Exercise 2.3

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2 parse trees for sentence abab, so the grammar is ambiguous.