PostScript – a quick way to visualize algorithms

# PostScript – a quick way to visualize algorithms

Sometimes (for example during a programming contest) there is a need of a quick tool for visualizing outcome of an algorithm.
PostScript might be a very useful tool then.

Here is a basic PostScript file:

```%!PS 3 setlinewidth % creating a square 200 200 moveto 400 200 lineto 400 400 lineto 200 400 lineto 200 200 lineto % drawing a square stroke % creating a circle located in (300,300) with radius 100 300 300 100 0 360 arc % drawing a square stroke showpage```

You should save it with extension .ps and open using Evince under Linux or GhostView under Windows.

Using this small set of commands: moveto, lineto, stroke, showpage, you can quickly vizualize your geometrical algorithms.
Here is example of creating an Archimedean spiral PostScript file in C++:

```#include <cstdio> #include <cstdlib> #include <cmath> using namespace std; FILE * fin;   void spiral(double xstart, double ystart, double radius, double a, double b){ fprintf(fin, "%f %f moveto\n", xstart+b, ystart); for(double fi=0.0; b+a*fi<=radius; fi+=0.1){ double r = b+a*fi, x = xstart + r*cos(fi), y = ystart + r*sin(fi); fprintf(fin, "%f %f lineto\n", x, y); }   }   int main(int argc, char ** argv){ double x, y, radius, a, b; if(argc!=6){ printf("USAGE: ./spiral X Y R A B\n"); x = 300; y=300; radius=200; a = 3; b= 40; } else{ x = atof(argv[1]); y=atof(argv[2]); radius = atof(argv[3]); a = atof(argv[4]); b = atof(argv[5]); } fin=fopen("spiral.ps", "w"); fprintf(fin, "%%!PS\n"); fprintf(fin, "3 setlinewidth\n"); spiral(x, y, radius, a, b); fprintf(fin, "stroke\n"); fprintf(fin, "showpage\n"); fclose(fin); return 0; }```

Parameter a adjusts “density” of lines in a spiral.
Parameter b adjusts “hole” in the center of a spiral.