Introduction to Metaprogramming

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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