One of the little things I found enjoyable while trying out Clojure was discovering the merge-with command. After counting the each of the subbranch and collecting the results in dictionaries, the dictionaries were merged together.

clojure.core/merge-with
([f & maps])
Returns a map that consists of the rest of the maps conj-ed onto
the first. [...]

I had printed out the list of functions and macros in the Clojure API page, and it filled out two A4 pages. Where to start though? I walked the entire clojure and clojure contrib directory and counted the number of function calls. Here are the top stats.

sym count len
clojure.core/list 3872 17
quote 2749 5
defn 1757 4
clojure.core/seq 1481 16
clojure.core/concat 1480 19
= 1074 1
let 1042 3
is 885 2
. 836 1
if 826 2
defmethod 431 9
def 407 3
complex 377 7
defn- 376 5
fn 356 2
first 346 5
defmacro 298 8
clojure.core/apply 264 18
deftest 257 7
str 252 3
when 244 4
imaginary 238 9
recur 237 5
apply 229 5
instance? 220 9
nil 217 3
and 214 3
next 208 4
cl-format 206 9
fn* 197 3
ns 194 2
map 193 3
:use 187 4
list 184 4
1 181 1
count 178 5
+ 169 1
seq 167 3
reduce 165 6
are 148 3
cons 143 4
println 141 7
or 141 2
not 135 3
loop 133 4
thrown? 127 7
* 127 1
conj 125 4
print 124 5
nth 124 3
- 116 1
doseq 114 5

Now, I have a study-plan.
Incidentally, waterfront IDE is quite [...]