Take a break to make a snake!

ECMAScript 6 Javascript (399 401 431)

Has to be run in a browser supporting ECMAScript 6 due to the arrow functions.

Here are fiddles which have been altered to run in any (common) browser by not using arrow functions. They also print to a textarea instead:

  • Normal
  • Animated

Golfed Version

i=prompt(),v=[],c=0,x=[0],y=[0],s='unshift',k='slice',t='sort',h=[0,-1,0,1,0]
while(c<i.length){m='wasd'.indexOf(i[c++]);v[s]('^<v>'[m]);x[s](x[0]+h[m]);y[s](y[0]+h[m+1])}f=(a,b)=>a-b
q=x[k]()[t](f)[0],e=x[k]()[t]((a,b)=>b-a)[0],w=y[k]()[t](f)[0],o=[]
while((i=y.pop())!=null){i-=w;j=x.pop()-q;t=(o[i]||Array(e+1-q).join(" ")).split("");t.splice(j,1,v.pop()||"@");o[i]=t.join("")}alert(o.join("\n"))

Animated GIF:

One of the OP's examples:

enter image description here

The example from Stretch Maniac:

enter image description here

Ungolfed

Here is a (slightly) ungolfed version from sometime before I started really golfing it down:

var input = prompt(),
    values = [],
    c = 0,
    x = [0],
    y = [0],
    s = 'unshift';
while (c < input.length) {
    var mapped = 'wasd'.indexOf(input[c++]);
    values[s]('^<v>'[mapped]);
    x[s](x[0]+[0, -1, 0, 1][mapped]);
    y[s](y[0]+[-1, 0, 1, 0][mapped]);
}

var minX = x.slice().sort(function (a,b){return a-b})[0];
var maxX = x.slice().sort(function (a,b){return b-a})[0];
var minY = y.slice().sort(function (a,b){return a-b})[0];

var output = [];
while((i=y.pop())!=null) {
    i-=minY;
    j=x.pop()-minX;
    t=(output[i]||Array(maxX+1-minX).join(" ")).split("");
    t.splice(j,1,values.pop()||"@");
    output[i]=t.join("");    
}

console.log(output.join("\n"));

sed, 71

s/w/\^\x1B[D\x1B[A/g
s/a/<\x1B[2D/g
s/s/v\x1B[B\x1B[D/g
s/d/>/g
s/$/@/

Golfscript, 165 126

' '*"\33[":e{e'D'}:-{[e'C'+'<'--]]}:a{[-+'>']]}:d{[e'B'+'^'-e'A']]}:w{[e'A'+'v'-e'B']]}:s{][\[}:+7{;}*''\~[e'H'e'J']\'@'e'20H'

Same approach as my previous answer, but correctly positioning the cursor before and afterwards. I'm pretty proud of the approach to cursor positioning -- basically, it first runs the snake in reverse, without printing out characters.


Ruby, 207 characters

b=[];x=y=0;gets.chars{|c|b[y]||=[];b[y][x]={?\n=>->{?0},?w=>->{y>0?y-=1:b=[[]]+b;?^},?a=>->{x>0?x-=1:b.map!{|r|[' ']+r};b[y][1]=?<},?s=>->{y+=1;?v},?d=>->{x+=1;?>}}[c][]};puts b.map{|r|r.map{|c|c||' '}.join}

Ungolfed:

b=[]  #board
x=y=0 #position
gets.each_char{|c|
  b[y] ||= []
  b[y][x] = {
    "\n" => lambda{0},
    "w"  => lambda{if y>0 then y-=1 else b=[[]]+b; "^"},
    "a"  => lambda{if x>0 then x-=1 else b.map!{|r|[' ']+r}; b[y][1]="<"},
    "s"  => lambda{y+=1; "v"},
    "d"  => lambda{x+=1; ">"}
  }[c].call}
puts b.map{|r|r.map{|c|c||' '}.join}

(the lambda for a writes back because the row the assignment above writes to is no longer on the board)

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