Tips for golfing in Jelly Jelly is a tacit, golf-oriented programming language by our very own Dennis. It’s popping up in answers here more and more often, beating other golf-y languages like Pyth and CJam, both by using its own code page and its powerful chain system to succinctly express programs.

Let’s collect some useful tips for golfing in Jelly. (As always, one tip per answer, please!)
String compression


  If you're looking for a more optimized/automatic string compressor, try this one.


Try it online!

A compressed string looks like “...», where the dots are a chunk of base-250-encoded data. The decompression algorithm is a bit complicated: the chunk is interpreted as a “mixed-base” integer, with divmod breaking off various parts of this integer and constructing a string out of them.

I’ve created a little Python 3 interface to compress Jelly strings:



import dictionary
code_page = '''¡¢£¤¥¦©¬®µ½¿€ÆÇÐÑ×ØŒÞßæçðıȷñ÷øœþ !"#$%&amp;'()*+,-./0123456789:;&lt;=&gt;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~¶°¹²³⁴⁵⁶⁷⁸⁹⁺⁻⁼⁽⁾ƁƇƊƑƓƘⱮƝƤƬƲȤɓƈɗƒɠɦƙɱɲƥʠɼʂƭʋȥẠḄḌẸḤỊḲḶṂṆỌṚṢṬỤṾẈỴẒȦḂĊḊĖḞĠḢİĿṀṄȮṖṘṠṪẆẊẎŻạḅḍẹḥịḳḷṃṇọṛṣṭụṿẉỵẓȧḃċḋėḟġḣŀṁṅȯṗṙṡṫẇẋẏż«»‘’“”'''

class Compress(list):
    def character(self, c):
        if c in '\n\x7f¶':
            o = 95
        elif ' ' &lt;= c &lt;= '~':
            o = ord(c)-32
        else:
            raise ValueError(c + " is neither printable ASCII nor a linefeed.")
        self += [lambda z: 3*z+0, lambda z: 96*z+o]; return self
    def string(self, s):
        for c in s: self.character(c)
        return self
    def dictionary(self, w):
        ts = bool(self)
        if w[:1] == ' ': w = w[1:]; ts = not ts
        dct = dictionary.short if len(w) &lt; 6 else dictionary.long
        W, sc = (w, 0) if w in dct else (w[:1].swapcase() + w[1:], 1)
        if W not in dct: raise ValueError(w + " isn't in the dictionary.")
        f = ts or sc; j = (2 if sc else 1) if ts else 0; i = dct.index(W)
        self += [lambda z: 3*z+2, lambda z: 3*z+j] if f else [lambda z: 3*z+1]
        self += [lambda z: 2*z+int(len(w) &lt; 6), lambda z: len(dct)*z+i]
        return self
    def go(self):
        compressed = []; z = 0
        for f in self[::-1]: z = f(z)
        while z:
            c = z % 250
            if c == 0: c = 250
            z = (z - c) // 250
            compressed.append(code_page[c - 1])
        return '“{0}»'.format(''.join(compressed[::-1]))


Use the compressor as follows.

print(Compress()
      .dictionary('public')
      .dictionary(' static')
      .dictionary(' boolean')
      .string(' is')
      .dictionary('Power')
      .string('Of')
      .dictionary('Ten')
      .string('(')
      .dictionary('long')
      .dictionary(' input')
      .string(') {\n ')
      .dictionary(' return')
      .string('\n   ')
      .dictionary(' input')
      .string(' ==')
      .go())


Compress is a string builder:


.string(s) will insert raw, printable ASCII characters into the string.

(Each character costs about 0.827 compressed bytes.)
.dictionary(w) will look up a string in Jelly’s built-in dictionaries. You may begin the string with a single space, if you want one. If this needs to deviate from the normal string-adding behavior, or flip the capitalization of a dictionary word, it’ll add flags accordingly.

(Costs about 1.997 bytes for short words, 2.433 bytes for long words; if there are flags, add 0.199 bytes.)