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δΣω Ϩ ʔ λ Λ
༗ ޮ ׆ ༻ ͠ ୂ
2 0 1 6 - 1 0 - 2 2 K y o t o . j s 1 1
Twitter @susisu2413 / GitHub @susisu
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Q .
δΣω Ϩ ʔ λ
Կ ʹ ͑Δʁ
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1 . ί ϧ ʔ νϯ
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app.use(function* (next) {
const start = new Date(); // (1)
yield next;
const end = new Date(); // (3)
// log (4)
});
!
app.use(function* (next) {
yield next;
// respond (2)
});
ྫ: Koa
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2 . Ԇ Ϧε τ
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function range(a, b, s = 1) {
const arr = [];
for (let n = a; n < b; n += s) {
arr.push(n);
}
return arr;
}
!
for (const n of range(1, 10)) {
doSomething(n); // from 1 to 9
}
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function* xrange(a, b, s = 1) {
for (let n = a; n < b; n += s) {
yield n;
}
}
!
for (const n of xrange(1, 10)) {
doSomething(n); // from 1 to 9
}
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function* fibonacci() {
let [a, b] = [1, 1];
while (true) {
yield a;
[a, b] = [b, a + b];
}
}
!
for (const n of fibonacci()) {
doSomething(n); // 1, 1, 2, 3, 5, ...
}
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3 . Π ς Ϩ ʔ λ ͷ Ճ
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function* concat(iter1, iter2) {
yield* iter1;
yield* iter2;
}
!
for (const x of concat(arr1, arr2)) {
doSomething(x);
}
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function* map(func, iter) {
for (const x of iter) {
yield func(x);
}
}
!
for (const n of map(n => n ** 2, arr)) {
doSomething(n);
}
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4 . ඇ ಉ ظ ॲ ཧ
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fetch().then(x =>
fetch().then(y =>
fetch().then(z =>
doSomething(x, y, z)
)
)
);
before (Promise)
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co(function* () {
const x = yield fetch();
const y = yield fetch();
const z = yield fetch();
return doSomething(x, y, z);
});
after (Promise + Generator + co)
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Q .
ଞ ʹ δΣω Ϩ ʔ λ ͕
͑Δ ໘ ͋ Δʁ
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ͦ ͦ δΣω Ϩ ʔ λ ͱ
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g e n . n e x t ( )
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{ d o n e : f a l s e ,
v a l u e : * }
g e n . n e x t ( )
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{ d o n e : f a l s e ,
v a l u e : * }
g e n . n e x t ( )
g e n . n e x t ( )
gen.next ͷதมΘ͍ͬͯΔ
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{ d o n e : f a l s e ,
v a l u e : * }
{ d o n e : f a l s e ,
v a l u e : * }
g e n . n e x t ( )
g e n . n e x t ( )
g e n . n e x t ( )
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{ d o n e : f a l s e ,
v a l u e : * }
{ d o n e : f a l s e ,
v a l u e : * }
{ d o n e : t r u e ,
v a l u e : * }
g e n . n e x t ( )
g e n . n e x t ( )
g e n . n e x t ( )
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ݟํΛม͑Δͱ͍͔ʹԆϦετ
d o n e : f a l s e
v a l u e ( ) = > d o n e : f a l s e
v a l u e ( ) = > d o n e : t r u e
v a l u e
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d o n e : f a l s e
v a l u e x = > d o n e : f a l s e
v a l u e y = > d o n e : t r u e
v a l u e
.next() ҾΛͱΕΔ
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fetch().then(x =>
fetch().then(y =>
fetch().then(z =>
doSomething(x, y, z)
)
)
);
PromiseΛͬͨඇಉظॲཧ
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No content
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d o n e : f a l s e
v a l u e x = > d o n e : f a l s e
v a l u e y = > d o n e : t r u e
v a l u e
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t h e n
v a l u e x = > t h e n
v a l u e y = > re s o l v e
v a l u e
.then() Ͱͭͳ͗߹ΘͤΔ
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co(function* () {
const x = yield fetch();
const y = yield fetch();
const z = yield fetch();
return doSomething(x, y, z);
});
Promise + Generator + co
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Q .
ଞ ʹ δΣω Ϩ ʔ λ ͕
͑Δ ໘ ͋ Δʁ
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A .
͋ Γ · ͢
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5 . ύ ʔ α ί ϯ Ϗω ʔ λ
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symbol("(").bind(_ =>
expr.bind(x =>
symbol(")").bind(_ =>
pure(x)
)
)
);
ׅހ (ʙ) ʹೖͬͨࣜͷύʔα
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qo(function* () {
yield symbol("(");
const x = yield expr;
yield symbol(")");
return x;
});
దͳؔΛ͑……
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6 . * ద ͳ Ϟ φ υ
※ Ͳ ΕͰ ྑ ͍ ͱ ͍ ͏ Θ ͚ Ͱ ͳ ͍
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δΣω Ϩ ʔ λ Λ
༗ ޮ ׆ ༻ ͠ ୂ
׆ ಈ ใ ࠂ
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δΣω Ϩ ʔ λ
Ԇ Ϧε τ Λ
Ұ ൠ Խ ͠ ͨ Α ͏ ͳ ͷ
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· ͩ · ͩ
͑Δ ໘ ͕ ͋ Γ ͦ ͏
ྫ : ύ ʔ α ί ϯ Ϗω ʔ λ
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ଞ ʹ ׆ ༻ ࣄ ྫ ͕ ͋ Ε
͓ ڭ ͑͘ ͩ ͞ ͍
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{ d o n e : t r u e ,
v a l u e : " T h a n k s " }