Logo Implementation Using Flex

logo.l

%{ 
#include <math.h>
#define PI 3.14159

float distance = 0;
float location[2]; // current coordinates (x, y)
float angle_x = PI/2; // current angle with positive X-axis

double displacement(double x, double y){
	return sqrt(x*x + y*y);
}

%}

DIGIT [0-9]
ALPHABET [A-Za-z]
SPACE ' '

%% 
STOP {return 0;}
FD" "({DIGIT}*"."{DIGIT}+|{DIGIT}+) {
	float temp = atof(&yytext[3]);
	printf("MOVE FORWARD BY %f UNITS\n", temp);
	location[0] += cos(angle_x) * temp;
	location[1] += sin(angle_x) * temp;
	distance += temp;
	printf("NEW LOCATION: (%f, %f)\n", location[0], location[1]);
}

BK" "({DIGIT}*"."{DIGIT}+|{DIGIT}+) {
	float temp = atof(&yytext[3]);
	printf("MOVE BACKWARD BY %f UNITS\n", temp);
	location[0] -= cos(angle_x) * temp;
	location[1] -= sin(angle_x) * temp;
	distance += temp;
	printf("NEW LOCATION: (%f, %f)\n", location[0], location[1]);
}

RT" "({DIGIT}*"."{DIGIT}+|{DIGIT}+) {
	float temp = atof(&yytext[3]);
	printf("TURN RIGHT BY %f DEGREES\n", temp);
	angle_x -= (temp * PI)/180;
	printf("Angle with +X Axis: %f degrees\n", (180/PI) * angle_x);
}
LT" "({DIGIT}*"."{DIGIT}+|{DIGIT}+) {
	float temp = atof(&yytext[3]);
	printf("TURN LEFT BY %f DEGREES\n", temp);
	angle_x += (temp * PI)/180;
	printf("Angle with +X Axis: %f degrees\n", (180/PI) * angle_x);
}

{DIGIT}*"."{DIGIT}+ {
	printf("Floating point number %s (%f)\n", yytext, atof(yytext));
}
{DIGIT}+ {
	printf("An integer %s, (%d)\n", yytext, atoi(yytext));
}
SPACE { /** Do nothing **/ }
{ALPHABET}+ {printf("[ERROR] Don't know how to %s.\n", yytext);}
%% 
  
int yywrap(){} 
int main(){
	yylex(); 
	printf("\nTotal distance - %f\n", distance);
	printf("\nTotal displacement - %f\n", displacement(location[0], location[1]));
	return 0;
}

runlex.sh

FILENAME=$1
flex $FILENAME
gcc lex.yy.c -lm
./a.out