This document defines a macro called my_macro in Clojure that takes a predicate and list of arguments and conditionally executes the arguments if the predicate returns true. It demonstrates calling my_macro with (= 1 2) which returns false and doesn't print "hello", but with (= 1 1) which returns true and prints "hello". It also shows compiling my_macro into a function that can be called directly later.

2. lagénorhynque
(def fi e ag h e
:id @ age h e
: eadi g "/ a e ɛ̃/"
:a ia e [" "]
: a g age [C e Ha e E g i h f a ai ]
:i e e [ g a i g a g age- ea i g a a he a ic ]
:c i ["gi h b.c / age h e/d c . d e. ede a "
"gi h b.c / age h e/d c . d e.ca bi "]
:c ib e ["gi h b.c / a a -c ia /c e- i e- a"])

3. 1.
2.
3.
/

5. ( )
metaprogramming
R b 2

6. (
)
( )
( )
e c.
(
)
( )
( )
e c.
e ec i
me acla
em la e
mac

8. /
/
e c.
DSL ( )
e c.
d mai - eci c la g age

9. e c.
e c.

10. e g
Macro Club has t o rules, plus one
e ception. The rst rule of Macro Club
is Don t Write Macros. (...) The second
rule of Macro Club is Write Macros f
That s the Onl Wa to Encapsulate a
Pattern. (...) The e ception to the rule
is that ou can rite an macro that
makes life easier for our callers
hen compared ith an equi alent
function.

13. , Java
Class Method
he > c a G ee i g
...> i a e S i g a e;
...> G ee i g(S i g a e)
...> hi . a e = a e;
...>
...> S i g he ()
...> e "He , " + a e + "!";
...>
...> i a e S i g b ()
...> e "B , " + a e + " !";
...>
...>
c ea ed c a G ee i g

14. he > a g = e G ee i g(" ag h e")
g ==> G ee i g@377dca04
he > g.he ()
$3 ==> "He , ag h e!"
he > g.b ()
E :
b () ha i a e acce i G ee i g
g.b ()
^-------^

15. he > G ee i g.c a .ge Dec a edMe h d ()
$4 ==> Me h d[2] a a. a g.S i g G ee i g.he (), i a e a
a. a g.S i g G ee i g.b ()
he > a He = G ee i g.c a .ge Dec a edMe h d("he ")
He ==> a a. a g.S i g G ee i g.he ()
he > He .i e(g)
$6 ==> "He , ag h e!"

16. he > a B = G ee i g.c a .ge Dec a edMe h d("b
")
B ==> i a e a a. a g.S i g G ee i g.b ()
he > B .i e(g)
E ce i a a. a g.I ega Acce E ce i : c a REPL.$JShe
a Ref ec i . e I ega Acce E ce i (Ref ec i . a a
a Acce ib eOb ec .chec Acce (Acce ib eOb ec . a a:6
a Me h d.i e (Me h d. a a:556)
a (#10:1)
he > B . e Acce ib e( e)
he > B .i e(g)
$12 ==> "B , ag h e !"

17. (R b )
(P h )
e d
ge a

18. Ruby
method missing
i b( ai ):001:1* c a G ee i g
i b( ai ):002:2* def i i ia i e( a e)
i b( ai ):003:2* @ a e = a e
i b( ai ):004:1* e d
i b( ai ):005:2* def e h d_ i i g( , *a g )
i b( ai ):006:2* "# .ca i a i e , # @ a e !"
i b( ai ):007:1* e d
i b( ai ):008:1* e d
=> : e h d_ i i g
i b( ai ):009:0> g = G ee i g. e (" ag h e")
=> #<G ee i g:0 00007fcb472e0198 @ a e=" ag h e">
i b( ai ):010:0> g.he
=> "He , ag h e!"
i b( ai ):011:0> g.b
=> "B , ag h e!"

19. (P h )
__ge a __

21. open class Ruby
i b( ai ):001:1* c a S i g
i b( ai ):002:2* def he
i b( ai ):003:2* "He , # e f !"
i b( ai ):004:1* e d
i b( ai ):005:1* e d
=> :he
i b( ai ):006:0> " ag h e".he
=> "He , ag h e!"

22. Ruby
refinements
i b( ai ):001:1* d e G ee i g
i b( ai ):002:2* efi e S i g d
i b( ai ):003:3* def he
i b( ai ):004:3* "He , # e f !"
i b( ai ):005:2* e d
i b( ai ):006:1* e d
i b( ai ):007:0> e d
=> #< efi e e :S i g@G ee i g>

23. i b( ai ):008:1* d e M
i b( ai ):009:1* i g G ee i g
i b( ai ):010:2* c a << e f
i b( ai ):011:3* def f( a e)
i b( ai ):012:3* a e.he
i b( ai ):013:2* e d
i b( ai ):014:1* e d
i b( ai ):015:0> e d
=> :f

24. i b( ai ):016:0> M.f(" ag h e")
=> "He , ag h e!"
i b( ai ):017:0> " ag h e".he
T acebac ( ece ca a ):
4: f /U e / age h e/. be / e i /3.0.0/bi /i b
3: f /U e / age h e/. be / e i /3.0.0/bi /i b
2: f /U e / age h e/. be / e i /3.0.0/ ib/ b
1: f (i b):17:i `< ai >'
N Me h dE ( defi ed e h d `he ' f " ag h e":S i

25. e (Ja aSc i )
(Scala)
im lici cla

26. Ruby
i b( ai ):001:0> a e = " ag h e"
=> " ag h e"
i b( ai ):002:1* def a e.he
i b( ai ):003:1* "He , # e f !"
i b( ai ):004:1* e d
=> :he
i b( ai ):005:0> a e.he
=> "He , ag h e!"
i b( ai ):006:0> " ag h e".he
T acebac ( ece ca a ):
4: f /U e / age h e/. be / e i /3.0.0/bi /i b
3: f /U e / age h e/. be / e i /3.0.0/bi /i b
2: f /U e / age h e/. be / e i /3.0.0/ ib/ b
1: f (i b):6:i `< ai >'
N Me h dE ( defi ed e h d `he ' f " ag h e":S i

27. (P h )
(Ja aSc i )
(Cl j e)
Me h dT e

29. Clojure
e => (def ac e [ e & b d ]
`( he ( e )
@b d ))
#' e / e

30. e => ( e (= 1 2)
( i " e a "))
e a
i
e => ( e (= 1 1)
( i " e a "))
i

31. e => ( ac e a d-1
'( e (= 1 2)
( i " e a ")))
(c e.c e/ he (c e.c e/ (= 1 2)) ( i " e a
"))

32. Elixir
ie (1)> def d e M d
...(1)> def ac e ( e , d : b d ) d
...(1)> e d
...(1)> if ! e( e ) d
...(1)> e(b d )
...(1)> e d
...(1)> e d
...(1)> e d
...(1)> e d
: d e, M,
<<70, 79, 82, 49, 0, 0, 5, 120, 66, 69, 65, 77, 65, 116, 85, 56,
0, 0, 0, 17, 8, 69, 108, 105, 120, 105, 114, 46, 77, 8, 95, 95
102, 111, 95, 95, 10, 97, 116, 116, 114, ...>>, : e , 2

33. ie (2)> e i e M
M
ie (3)> M. e 1 == 2 d
...(3)> IO. " e a "
...(3)> e d
e a
:
ie (4)> M. e 1 == 1 d
...(4)> IO. " e a "
...(4)> e d
i

34. ie (5)> e d
...(5)> M. e 1 == 1 d
...(5)> IO. " e a "
...(5)> e d
...(5)> e d > Mac .e a d_ ce(__ENV__) >
...(5)> Mac . _ i g > IO.
if(!(1 == 1)) d
IO. (" e a ")
e d
:

35. R
J lia
Tem la e Ha kell
Scalame a
Mac P
H
S ee .j

37. Further Reading
DSL
R b 2
R b T
P h