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// JavaScript
const list = [1, 2, 3, 4, 5]
const odd_numbers = []
// 挑出奇數
for (let i = 0; i < list.length; i++) {
const el = list[i]
if (el % 2 === 1) {
odd_numbers.push(el)
}
}
const triple_numbers = []
// 乘 3 倍
for (let i = 0; i < odd_numbers.length; i++) {
triple_numbers.push(odd_numbers[i] * 3)
}
let total = 0
// 計算總和
for (let i = 0; i < triple_numbers.length; i++) {
total += triple_numbers[i]
}
console.log(total) // 27
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ޒഒላӃ
+4
// JavaScript
const list = [1, 2, 3, 4, 5]
const result = list.filter(i => i % 2 === 1)
.map(i => i * 3)
.reduce((acc, cv) => acc + cv, 0)
console.log(result) // 27
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ޒഒላӃ
+4
// JavaScript
const list = [1, 2, 3, 4, 5]
const oddOnly = (i) => i % 2 === 1
const triple = (i) => i * 3
const sum = (acc, cv) => acc + cv
const result = list.filter(oddOnly)
.map(triple)
.reduce(sum, 0)
console.log(result) // 27
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ॄኄੋ'1ʁ
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1SPHSBNNJOH1BSBEJHNT
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0CKFDU0SJFOUFE1SPHSBNNJOH
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ޒഒላӃ
෧ঝ
&ODBQTVMBUJPO*OIFSJUBODF
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ޒഒላӃ
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'VODUJPOBM1SPHSBNNJOH
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ޒഒላӃ
വᏐ
'VODUJPO
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ޒഒላӃ
ॄኄੋവᏐʁ
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ޒഒላӃ
f(x) = 3x + 2
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ޒഒላӃ
വᏐ༌ೖ值ᢛ༌ग़值೭ؒత᮫
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७വᏐ
1VSF'VODUJPO
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ޒഒላӃ
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# 不純
def one_weeks_later
Time.now + 7.days
end
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# 比較純
def one_weeks_later(current_time)
current_time + 7.days
end
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1VSF'VODUJPO
ෆ။㐫ଶվᏓ
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ޒഒላӃ
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# 不純
def add_book
Book.create(title: '為你⾃⼰學 Ruby')
end
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# 不純
def replace_element(arr, idx, value)
arr[idx] = value
arr
end
list = [1, 2, 3]
result = replace_element(list, 0, "a")
p result # ["a", 2, 3]
p list # ???
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ޒഒላӃ
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# 比較純
def replace_element(arr, idx, value)
dup_arr = arr.dup
dup_arr[idx] = value
dup_arr
end
list = [1, 2, 3]
result = replace_element(list, 0, "a")
p result # ["a", 2, 3]
p list # ???
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ޒഒላӃ
ෆՄᏓੑ
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ޒഒላӃ
+4
// JavaScript
const list = [1, 2, 3]
const otherList = list
console.log(list) // [1, 2, 3]
otherList[0] = "a"
console.log(list) // ???
ޒഒላӃ
+4
def add_numbers(a, b, c)
a + b + c
end
# 柯⾥化
curried_add = -> (x) {
-> (y) {
-> (z) {
add_numbers(x, y, z)
}
}
}
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# 分開寫
add_2 = curried_add.call(2)
add_3 = add_2.call(3)
result = add_3.call(5)
puts result
# 或串在⼀起寫
puts curried_add.call(2).call(3).call(5)
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ޒഒላӃ
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def add_numbers(a, b, c)
a + b + c
end
# 柯⾥化
# curried_add = -> (x) {
# -> (y) {
# -> (z) {
# add_numbers(x, y, z)
# }
# }
# }
# Ruby 內建的⽅法
curried_add = method(:add_numbers).curry
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ภവᏐ
1BSUJBM'VODUJPOT
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ޒഒላӃ
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ჩᏐɼճၚडႫᰨჩᏐత৽വᏐ
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ޒഒላӃ
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def add_numbers(a, b, c)
a + b + c
end
# Partial Function
# 先給 1 個參數
add_2 = -> (i, j) { add_numbers(2, i, j) }
# 剩下的 2 個參數之後再⼀次給⾜
puts add_2.call(3, 5) # 10
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ޒഒላӃ
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def add_numbers(a, b, c)
a + b + c
end
# Partial Function
# 或是先給 2 個參數
add_2_and_3 = -> (k) { add_numbers(2, 3, k) }
# 最後 1 個參數之後再給
puts add_2_and_3.call(5) # 10
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def add_numbers(a, b, c)
a + b + c
end
# 利⽤內建的 curry ⽅法
partial_fn = method(:add_numbers).curry
# 先給 1 個參數
add_2 = partial_fn.call(2)
# 剩下的參數之後再⼀次給⾜
puts add_2.call(3, 5) # 10
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ޒഒላӃ
വᏐ߹
'VODUJPO$PNQPTJUJPO
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ઌՃɼ࠶Ճഒɼ࠷ޙ࠶ฏํʂ
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ޒഒላӃ
+4
// JavaScript
const add_one = (n) => n + 1
const double = (n) => n * 2
const square = (n) => n * n
console.log(square(double(add_one(5)))) // 144
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ޒഒላӃ
ઢ
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ޒഒላӃ
+4
# Elixir
add_one = fn x -> x + 1 end
double = fn x -> x * 2 end
square = fn x -> x * x end
result = 5 |> add_one.()
|> double.()
|> square.()
IO.inspect result # 144
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ޒഒላӃ
3VCZᔒ༗Ṝኄํศత౦
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ޒഒላӃ
+4
add_one = -> (n) { n + 1 }
double = -> (n) { n * 2 }
square = -> (n) { n * n }
# 先加 1，再加倍，最後再平⽅
composed_fn = add_one.compose(double)
.compose(square)
puts composed_fn.call(5) # 144