I don't really create programs anymore. Programs are restricted in what they can do. I thought for a while that I was instead creating libraries for programming. After a while though, I realized that wasn't the case either. To a certain degree, I try to think about my packages as domain specific languages. I think about creating a way to write out common concepts I need to express and build the underlying functionality in a way that will be flexible. Only after doing this a ton do I begin actually writing the thing I want.
Maybe this is just something I never really got about programming before.
But I'm not sure what it is I am really understanding except the concept of a programming language is still underrated.
MakeTurtle[] := Turtle[{0.,0.},0.,{}]; MakeTurtle[loc_,angle_,lines_]:=Turtle[loc,angle,lines];
Location[trtl_]:=trtl[[1]]; Angle[trtl_]:=trtl[[2]]; Lines[trtl_]:=trtl[[3]];
Move[trtl_,distance_]:=With[{newLoc = Location@trtl+distance*Cos[Angle@trtl],Sin[Angle@trtl]})},
MakeTurtle[newLoc,Angle@trtl,Append[Lines@trtl,Line[{Location@trtl,newLoc}]]]]
Move[distance_]:=Function[trtl,Move[trtl,distance]];
TurnRight[trtl_,angle_]:= MakeTurtle[Location@trtl,Angle@trtl+angle,Lines@trtl];
TurnRight[angle_]:=Function[trtl,TurnRight[trtl,angle]];
TurnLeft[trtl_,angle_]:= MakeTurtle[Location@trtl,Angle@trtl-angle,Lines@trtl];TurnLeft[angle_]:=Function[trtl,TurnLeft[trtl,angle]];
ShowTurtle[trtl_]:=Graphics@Lines@trtl;
trtl:=Nest[(#//TurnRight[RandomReal[{0,2Pi}]]//Move[RandomVariate[NormalDistribution[0,1]]])&,MakeTurtle[],300];