BasicInterpreter2.c

/* Problem statement at https://github.com/pangfengliu/programmingtasks/issues/270 */
#include<stdio.h>
#include<ctype.h>
#include<string.h>
#include<stdlib.h>
#include<assert.h>
#define MAX_VAR_LEN 8
#define MAX_VAR_NUM 100
#define MAX_LINE_NUM 1000
#define MAX_LINE_TOKENS 6
#define MAX_TOKEN_LEN 8
#define CODE_ZERO 48
typedef struct {
	char name[MAX_VAR_LEN];
	int value;
} var;

enum { NAME,VAR,EQSIGN };

enum { IF,GOTO,PRINT,ASSIGN,STOP };
int numOfOprand[5] = {5,1,1,4,0};

enum { EQ,LT,GT,ELT,EGT,NEQ};
const char* cmp[6] = {"==","<",">","<=",">=","!="};
int numOfCmp = 6 ;

enum {ADD,SUB,MUL,DIV,MOD};
const char* op[5] = {"+","-","*","/","%"};
int numOfOp = 5 ;

char tokens[MAX_LINE_NUM*MAX_LINE_TOKENS][MAX_TOKEN_LEN];
int lineFirstTokIndex[MAX_LINE_NUM+1] = {0};

var vars[MAX_VAR_NUM] ;
int numOfVars ;

int parseInt(char* s){
	int result = 0 ;
	while(*s!='\0'){
		result = result*10 + *s - CODE_ZERO;
		s++;
	}
	return result;
}
int classifyVar(char* token){
	if(*token == '=')
		return EQSIGN;
	if(*token == '-' )
		return VAR;
	int i;
	int len = strlen(token);
	for(i=0;i<len;i++)
		if(!isdigit(token[i]))
			return NAME;
	return VAR;
}
int classifyCmd(char* cmd){
	if(!strcmp(cmd,"IF"))
		return IF;
	if(!strcmp(cmd,"GOTO"))
		return GOTO;
	if(!strcmp(cmd,"PRINT"))
		return PRINT;
	if(!strcmp(cmd,"STOP"))
		return STOP;
	return ASSIGN;
}
int do_Op(char* inOp,int a,int b){
	if(!strcmp(inOp,"+"))
		return a+b;
	if(!strcmp(inOp,"-"))
		return a-b;
	if(!strcmp(inOp,"*"))
		return a*b;
	if(!strcmp(inOp,"/"))
		return a/b;
	if(!strcmp(inOp,"%"))
		return a%b;
	printf("Operation no match!\n");
	return 0;
}
int do_Cmp(char* inCmp,int a,int b){
	if(!strcmp(inCmp,"=="))
		return a==b;
	if(!strcmp(inCmp,"<"))
		return a<b;
	if(!strcmp(inCmp,">"))
		return a>b;
	if(!strcmp(inCmp,"<="))
		return a<=b;
	if(!strcmp(inCmp,">="))
		return a>=b;
	if(!strcmp(inCmp,"!="))
		return a!=b;
	printf("Compare no match!\n");
	return 0;
}
var* findVar(char* target){
	int i;
	for (i = 0; i < numOfVars; ++i)
		if(!strcmp(vars[i].name,target))
			return &vars[i];
	printf( "Target:%s, not found",target );
}
int do_assignment(int index){
	var* target = findVar(tokens[index]);
	var* oprand1 = findVar(tokens[index+2]);
	var* oprand2 = findVar(tokens[index+4]);
	(*target).value = do_Op(tokens[index+3],(*oprand1).value,(*oprand2).value);
	return index + numOfOprand[ ASSIGN ] + 1;
}
int do_print(int index){
	var* target = findVar(tokens[index+1]);
	printf("%d\n",(*target).value);
	return index + numOfOprand[ PRINT ] + 1;
}
int do_goto(int index){
	int goToLine = parseInt(tokens[index+1]);
	return lineFirstTokIndex[ goToLine ] ;
}
int do_if(int index){
	var* oprand1 = findVar(tokens[index+1]);
	var* oprand2 = findVar(tokens[index+3]);
	if( do_Cmp(tokens[index+2],(*oprand1).value,(*oprand2).value) )
		return do_goto(index+4);
	else
		return index + numOfOprand[ IF ] + 1;
}
void readLine(int n,int i){
	while(n--){
		scanf("%s",tokens[i++]);
	}	
}
int main(int argc, char const *argv[])
{
	
	char token[MAX_VAR_LEN];
	numOfVars = 0;
	// read variable
	while( scanf("%s",token) && strcmp(token,"END")!=0 ){
		switch(classifyVar(token)){
			case NAME:
				strcpy(vars[numOfVars].name,token);
				break;
			case VAR:
				vars[numOfVars++].value = parseInt(token);
				break;

		}
	}
	int lineNum = 1;
	int i = 0 ;
	int cmdType;
	//Read the first token of a line
	while( scanf("%s",tokens[i]) ){

		cmdType = classifyCmd(tokens[i]);
		//Depending on the type of first token , read its operants
		readLine(numOfOprand[ cmdType ],i+1);
		
		//Mark line number
		lineFirstTokIndex[lineNum++] = i;
		i+=numOfOprand[ cmdType ]+1;
		if(cmdType == STOP )
			break;
	}
	i = 0;
	int done = 0 ;
	while(!done){
		switch(classifyCmd(tokens[i])){
			case ASSIGN:
				i = do_assignment(i);
				break;
			case GOTO:
				i = do_goto(i);
				break;
			case PRINT:
				i = do_print(i);
				break;
			case IF:
				i = do_if(i);
				break;
			case STOP:
				done = 1;
				break;
		}			
	}
	return 0;
}