Asymptote: Logical Operators and Loops

Asymptote (Vector Graphics Language)

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Asymptote uses loops and logical operators that are almost identical to those in C++. Loops are absolutely essential if you want to make diagrams that look like this:

This particular example was produced with the following code:

import graph;
real r=5; 
size(r*cm);
picture smiley;
filldraw(smiley,Circle((0,0),1),yellow,black);
fill(smiley,Circle((-.3,.4),.1),black);
fill(smiley,Circle((.3,.4),.1),black);
draw(smiley,Arc((0,0),.5,-140,-40));
for (int i=0; i<5; ++i)
{
 for (int j=0; j<5; ++j)
 {
  if (floor((i-j)/2)==((i-j)/2))
  {
  add(scale(r/10*cm)*smiley,(i,j));
  }
 }
}

Above, we created a picture called smiley and added it to currentpicture many times using a for loop, as the indices and each ranged from to . Basically, the arguments in the parentheses for the first for loop first declare to be an integer and assign to i the value . Then, if , it executes what is inside the {} brackets and when it is finished, it adds to (++i). This process repeats until the boolean statement has the value false, i.e. 5 times (hence the 5 columns of smileys). The if statement is self-explanatory; if (which checks if and have the same parity or not), then the smiley is added, and if not it skips the brackets that follow.