illustration of sieve of Eratosthenes

Author: gertingold

images/eratosthenes_1.pdf

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+import os
+import sys
+
+import numpy as np
+from pyx import canvas, color, path, text, unit
+
+def draw_grid():
+    c.stroke(path.rect(0, 0, 25, 2))
+    for n in range(24):
+        c.stroke(path.line(n+1, 0, n+1, 2))
+    c.stroke(path.line(0, 1, 25, 1))
+
+text.set(text.LatexRunner)
+text.preamble(r'\usepackage{arev}\usepackage[T1]{fontenc}')
+unit.set(xscale=1.2, wscale=2.5)
+
+c = canvas.canvas()
+c.fill(path.rect(0, 1, 2, 1), [color.grey(0.7)])
+c.text(0.5, 1.5, '0', [text.halign.center, text.valign.middle])
+c.text(1.5, 1.5, '1', [text.halign.center, text.valign.middle])
+basename = os.path.splitext(sys.argv[0])[0]
+baseprimes = [0, 2, 3, 5, 7]
+ncolor = len(baseprimes)-1
+cancelled = set([0, 1])
+for nr, baseprime in enumerate(baseprimes):
+    if nr == 0:
+        for n in range(2, 50):
+            x = n % 25
+            y = 2-(n//25)
+            c.text(x+0.5, y-0.5, str(n), [text.halign.center, text.valign.middle])
+    else:
+        cancelled.add(baseprime)
+        hvalue = 1.1*(nr-1)/(ncolor-1)
+        hvalue = hvalue-int(hvalue)
+        primecolor = color.hsb(hvalue, 1, 0.8)
+        x = baseprime % 25
+        y = 2-(baseprime//25)
+        c.fill(path.rect(x, y, 1, -1), [primecolor])
+        c.text(x+0.5, y-0.5, r'\textbf{%s}' % baseprime,
+               [text.halign.center, text.valign.middle, color.grey(1)])
+        for n in range(baseprime**2, 50, baseprime):
+            if not n in cancelled:
+                cancelled.add(n)
+                x = n % 25
+                y = 2-(n//25)
+                c.stroke(path.line(x, y-1, x+1, y), [primecolor])
+                c.stroke(path.line(x, y, x+1, y-1), [primecolor])
+    draw_grid()
+    c.writePDFfile('%s_%s' % (basename, nr+1))
+
+for n in range(50):
+    if not n in cancelled:
+        x = n % 25
+        y = 2-(n//25)
+        c.fill(path.rect(x, y, 1, -1), [color.hsb(0.15, 1, 0.8)])
+        c.text(x+0.5, y-0.5, r'\textbf{%s}' % n,
+               [text.halign.center, text.valign.middle, color.grey(1)])
+draw_grid()
+c.writePDFfile('%s_%s' % (basename, nr+2))
+