Merge 37fcf648ec into faa02b5fae
This commit is contained in:
frankiezdh
GitHub
commit
efa01ffbb9
9 changed files with 110 additions and 110 deletions
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@ -3,37 +3,37 @@
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(meditations
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"We shall contemplate truth by testing reality, via equality"
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(= __ true)
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(= true true)
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"To understand reality, we must compare our expectations against reality"
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(= __ (+ 1 1))
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(= 2 (+ 1 1))
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"You can test equality of many things"
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(= (+ 3 4) 7 (+ 2 __))
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(= (+ 3 4) 7 (+ 2 5))
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"Some things may appear different, but be the same"
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(= __ (= 2 2/1))
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(= true (= 2 2/1))
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"You cannot generally float to heavens of integers"
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(= __ (= 2 2.0))
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(= false (= 2 2.0))
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"But a looser equality is also possible"
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(= __ (== 2.0 2))
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(= true (== 2.0 2))
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"Something is not equal to nothing"
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(= __ (not (= 1 nil)))
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(= true (not (= 1 nil)))
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"Strings, and keywords, and symbols: oh my!"
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(= __ (= "hello" :hello 'hello))
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(= false (= "hello" :hello 'hello))
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"Make a keyword with your keyboard"
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(= :hello (keyword __))
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(= :hello (keyword :hello))
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"Symbolism is all around us"
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(= 'hello (symbol __))
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(= 'hello (symbol 'hello))
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"What could be equivalent to nothing?"
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(= __ nil)
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(= nil nil)
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"When things cannot be equal, they must be different"
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(not= :fill-in-the-blank __))
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(not= :fill-in-the-blank "" true nil))
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@ -4,67 +4,67 @@
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(meditations
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"A string is nothing more than text surrounded by double quotes"
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(= __ "hello")
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(= "hello" "hello")
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"But double quotes are just magic on top of something deeper"
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(= __ (str 'world))
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(= "world" (str 'world))
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"You can do more than create strings, you can put them together"
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(= "Cool right?" (str __ __))
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(= "Cool right?" (str "Cool" " right?"))
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"You can even get certain characters"
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(= \C (get "Characters" __))
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(= \C (get "Characters" 0))
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"Or even count the characters"
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(= __ (count "Hello World"))
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(= 11 (count "Hello World"))
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"But strings and characters are not the same"
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(= __ (= \c "c"))
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(= false (= \c "c"))
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"What if you only wanted to get part of a string?"
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(= "World" (subs "Hello World" __ __))
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(= "World" (subs "Hello World" 6 11))
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"How about joining together elements in a list?"
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(= __ (string/join '(1 2 3)))
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(= "123" (string/join '(1 2 3)))
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"What if you wanted to separate them out?"
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(= "1, 2, 3" (string/join __ '(1 2 3)))
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(= "1, 2, 3" (string/join ", " '(1 2 3)))
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"Maybe you want to separate out all your lines"
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(= [__ __ __] (string/split-lines "1\n2\n3"))
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(= ["1" "2" "3"] (string/split-lines "1\n2\n3"))
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"You may want to make sure your words are backwards"
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(= __ (string/reverse "hello"))
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(= "olleh" (string/reverse "hello"))
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"Maybe you want to find the index of the first occurrence of a substring"
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(= 0 (string/index-of "hello world" __))
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(= 0 (string/index-of "hello world" "h"))
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"Or maybe the last index of the same"
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(= __ (string/last-index-of "hello world, hello" "hello"))
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(= 13 (string/last-index-of "hello world, hello" "hello"))
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"But when something doesn't exist, nothing is found"
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(= __ (string/index-of "hello world" "bob"))
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(= nil (string/index-of "hello world" "bob"))
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"Sometimes you don't want whitespace cluttering the front and back"
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(= __ (string/trim " \nhello world \t \n"))
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(= "hello world" (string/trim " \nhello world \t \n"))
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"You can check if something is a char"
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(= __ (char? \c))
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(= true (char? \c))
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"But it may not be"
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(= __ (char? "a"))
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(= false (char? "a"))
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"But chars aren't strings"
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(= __ (string? \b))
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(= false (string? \b))
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"Strings are strings"
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(= true (string? __))
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(= true (string? ""))
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"Some strings may be blank"
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(= __ (string/blank? ""))
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(= true (string/blank? ""))
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"Even if at first glance they aren't"
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(= __ (string/blank? " \n \t "))
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(= true (string/blank? " \n \t "))
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"However, most strings aren't blank"
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(= __ (string/blank? "hello?\nare you out there?")))
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(= false (string/blank? "hello?\nare you out there?")))
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@ -3,43 +3,43 @@
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(meditations
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"Lists can be expressed by function or a quoted form"
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(= '(__ __ __ __ __) (list 1 2 3 4 5))
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(= '(1 2 3 4 5) (list 1 2 3 4 5))
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"They are Clojure seqs (sequences), so they allow access to the first"
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(= __ (first '(1 2 3 4 5)))
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(= 1 (first '(1 2 3 4 5)))
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"As well as the rest"
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(= __ (rest '(1 2 3 4 5)))
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(= '(2 3 4 5) (rest '(1 2 3 4 5)))
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"Count your blessings"
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(= __ (count '(dracula dooku chocula)))
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(= 3 (count '(dracula dooku chocula)))
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"Before they are gone"
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(= __ (count '()))
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(= 0 (count '()))
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"The rest, when nothing is left, is empty"
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(= __ (rest '(100)))
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(= '() (rest '(100)))
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"Construction by adding an element to the front is easy"
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(= __ (cons :a '(:b :c :d :e)))
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(= '(:a :b :c :d :e) (cons :a '(:b :c :d :e)))
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"Conjoining an element to a list isn't hard either"
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(= __ (conj '(:a :b :c :d) :e))
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(= '(:e :a :b :c :d) (conj '(:a :b :c :d) :e))
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"You can use a list like a stack to get the first element"
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(= __ (peek '(:a :b :c :d :e)))
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(= :a (peek '(:a :b :c :d :e)))
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"Or the others"
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(= __ (pop '(:a :b :c :d :e)))
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(= '(:b :c :d :e) (pop '(:a :b :c :d :e)))
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"But watch out if you try to pop nothing"
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(= __ (try
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(= "No dice!" (try
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(pop '())
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(catch IllegalStateException e
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"No dice!")))
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"The rest of nothing isn't so strict"
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(= __ (try
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(= '() (try
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(rest '())
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(catch IllegalStateException e
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"No dice!"))))
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@ -3,31 +3,31 @@
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(meditations
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"You can use vectors in clojure as array-like structures"
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(= __ (count [42]))
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(= 1 (count [42]))
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"You can create a vector from a list"
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(= __ (vec '(1)))
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(= [1] (vec '(1)))
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"Or from some elements"
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(= __ (vector nil nil))
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(= [nil nil] (vector nil nil))
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"But you can populate it with any number of elements at once"
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(= [1 __] (vec '(1 2)))
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(= [1 2] (vec '(1 2)))
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"Conjoining to a vector is different than to a list"
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(= __ (conj [111 222] 333))
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(= [111 222 333] (conj [111 222] 333))
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"You can get the first element of a vector like so"
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(= __ (first [:peanut :butter :and :jelly]))
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(= :peanut (first [:peanut :butter :and :jelly]))
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"And the last in a similar fashion"
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(= __ (last [:peanut :butter :and :jelly]))
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(= :jelly (last [:peanut :butter :and :jelly]))
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"Or any index if you wish"
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(= __ (nth [:peanut :butter :and :jelly] 3))
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(= :jelly (nth [:peanut :butter :and :jelly] 3))
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"You can also slice a vector"
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(= __ (subvec [:peanut :butter :and :jelly] 1 3))
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(= [:butter :and] (subvec [:peanut :butter :and :jelly] 1 3))
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"Equality with collections is in terms of values"
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(= (list 1 2 3) (vector 1 2 __)))
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(= (list 1 2 3) (vector 1 2 3)))
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@ -4,19 +4,19 @@
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(meditations
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"You can create a set by converting another collection"
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(= #{3} (set __))
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(= #{3} (set '(3)))
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"Counting them is like counting other collections"
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(= __ (count #{1 2 3}))
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(= 3 (count #{1 2 3}))
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"Remember that a set is a *mathematical* set"
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(= __ (set '(1 1 2 2 3 3 4 4 5 5)))
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(= #{1 2 3 4 5} (set '(1 1 2 2 3 3 4 4 5 5)))
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"You can ask clojure for the union of two sets"
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(= __ (set/union #{1 2 3 4} #{2 3 5}))
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(= #{1 2 3 4 5} (set/union #{1 2 3 4} #{2 3 5}))
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"And also the intersection"
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(= __ (set/intersection #{1 2 3 4} #{2 3 5}))
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(= #{2 3} (set/intersection #{1 2 3 4} #{2 3 5}))
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"But don't forget about the difference"
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(= __ (set/difference #{1 2 3 4 5} #{2 3 5})))
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(= #{1 4} (set/difference #{1 2 3 4 5} #{2 3 5})))
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@ -3,60 +3,60 @@
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(meditations
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"Don't get lost when creating a map"
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(= {:a 1 :b 2} (hash-map :a 1 __ __))
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(= {:a 1 :b 2} (hash-map :a 1 :b 2))
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"A value must be supplied for each key"
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(= {:a 1} (hash-map :a __))
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(= {:a 1} (hash-map :a 1))
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"The size is the number of entries"
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(= __ (count {:a 1 :b 2}))
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(= 2 (count {:a 1 :b 2}))
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"You can look up the value for a given key"
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(= __ (get {:a 1 :b 2} :b))
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(= 2 (get {:a 1 :b 2} :b))
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"Maps can be used as functions to do lookups"
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(= __ ({:a 1 :b 2} :a))
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(= 1 ({:a 1 :b 2} :a))
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"And so can keywords"
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(= __ (:a {:a 1 :b 2}))
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(= 1 (:a {:a 1 :b 2}))
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"But map keys need not be keywords"
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(= __ ({2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"} 2014))
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(= "Sochi" ({2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"} 2014))
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"You may not be able to find an entry for a key"
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(= __ (get {:a 1 :b 2} :c))
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(= nil (get {:a 1 :b 2} :c))
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"But you can provide your own default"
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(= __ (get {:a 1 :b 2} :c :key-not-found))
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(= :key-not-found (get {:a 1 :b 2} :c :key-not-found))
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"You can find out if a key is present"
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(= __ (contains? {:a nil :b nil} :b))
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(= true (contains? {:a nil :b nil} :b))
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"Or if it is missing"
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(= __ (contains? {:a nil :b nil} :c))
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(= false (contains? {:a nil :b nil} :c))
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"Maps are immutable, but you can create a new and improved version"
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(= {1 "January" 2 __} (assoc {1 "January"} 2 "February"))
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(= {1 "January" 2 "February"} (assoc {1 "January"} 2 "February"))
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"You can also create a new version with an entry removed"
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(= {__ __} (dissoc {1 "January" 2 "February"} 2))
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(= {1 "January"} (dissoc {1 "January" 2 "February"} 2))
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"Create a new map by merging"
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(= {:a 1 :b 2 __ __} (merge {:a 1 :b 2} {:c 3}))
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(= {:a 1 :b 2 :c 3} (merge {:a 1 :b 2} {:c 3}))
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"Specify how to handle entries with same keys when merging"
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(= {:a 1 :b __ :c 3} (merge-with + {:a 1 :b 1} {:b 1 :c 3}))
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(= {:a 1 :b 2 :c 3} (merge-with + {:a 1 :b 1} {:b 1 :c 3}))
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"Often you will need to get the keys, but the order is undependable"
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(= (list __ __ __)
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(= (list 2010 2014 2018)
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(sort (keys { 2014 "Sochi" 2018 "PyeongChang" 2010 "Vancouver"})))
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"You can get the values in a similar way"
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(= (list __ __ __)
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(= (list "PyeongChang" "Sochi" "Vancouver")
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(sort (vals {2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"})))
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"You can even iterate over the map entries as a seq"
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(= {:a __ :b __}
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(= {:a 2 :b 3}
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(into {}
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(map
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(fn [[k v]] [k (inc v)])
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|
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|
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@ -8,33 +8,33 @@
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(meditations
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"Calling a function is like giving it a hug with parentheses"
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(= __ (square 9))
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(= 81 (square 9))
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|
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"Functions are usually defined before they are used"
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(= __ (multiply-by-ten 2))
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(= 20 (multiply-by-ten 2))
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||||
|
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"But they can also be defined inline"
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(= __ ((fn [n] (* 5 n)) 2))
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(= 10 ((fn [n] (* 5 n)) 2))
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||||
|
||||
"Or using an even shorter syntax"
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(= __ (#(* 15 %) 4))
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(= 60 (#(* 15 %) 4))
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||||
|
||||
"Even anonymous functions may take multiple arguments"
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(= __ (#(+ %1 %2 %3) 4 5 6))
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(= 15 (#(+ %1 %2 %3) 4 5 6))
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||||
|
||||
"Arguments can also be skipped"
|
||||
(= __ (#(str "AA" %2) "bb" "CC"))
|
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(= "AACC" (#(str "AA" %2) "bb" "CC"))
|
||||
|
||||
"One function can beget another"
|
||||
(= 9 (((fn [] ___)) 4 5))
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(= 9 (#(+ %1 %2) 4 5))
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||||
|
||||
"Functions can also take other functions as input"
|
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(= 20 ((fn [f] (f 4 5))
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___))
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||||
#(* %1 %2)))
|
||||
|
||||
"Higher-order functions take function arguments"
|
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(= 25 (___
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(= 25 ((fn [f] (f 5))
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(fn [n] (* n n))))
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||||
|
||||
"But they are often better written using the names of functions"
|
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(= 25 (___ square)))
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(= 25 ((fn [f] (f 5)) square)))
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||||
|
|
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|||
|
|
@ -10,38 +10,38 @@
|
|||
|
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(meditations
|
||||
"You will face many decisions"
|
||||
(= __ (if (false? (= 4 5))
|
||||
(= :a (if (false? (= 4 5))
|
||||
:a
|
||||
:b))
|
||||
|
||||
"Some of them leave you no alternative"
|
||||
(= __ (if (> 4 3)
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(= [] (if (> 4 3)
|
||||
[]))
|
||||
|
||||
"And in such a situation you may have nothing"
|
||||
(= __ (if (nil? 0)
|
||||
(= nil (if (nil? 0)
|
||||
[:a :b :c]))
|
||||
|
||||
"In others your alternative may be interesting"
|
||||
(= :glory (if (not (empty? ()))
|
||||
:doom
|
||||
__))
|
||||
:glory))
|
||||
|
||||
"You may have a multitude of possible paths"
|
||||
(let [x 5]
|
||||
(= :your-road (cond (= x __) :road-not-taken
|
||||
(= x __) :another-road-not-taken
|
||||
:else __)))
|
||||
(= :your-road (cond (= x 1) :road-not-taken
|
||||
(= x 2) :another-road-not-taken
|
||||
:else :your-road)))
|
||||
|
||||
"Or your fate may be sealed"
|
||||
(= 'doom (if-not (zero? __)
|
||||
(= 'doom (if-not (zero? 1)
|
||||
'doom
|
||||
'more-doom))
|
||||
|
||||
"In case of emergency, go fast"
|
||||
(= "pretty fast"
|
||||
(explain-exercise-velocity __))
|
||||
(explain-exercise-velocity :bicycling))
|
||||
|
||||
"But admit it when you don't know what to do"
|
||||
(= __
|
||||
(= "is that even exercise?"
|
||||
(explain-exercise-velocity :watching-tv)))
|
||||
|
|
|
|||
|
|
@ -3,33 +3,33 @@
|
|||
|
||||
(meditations
|
||||
"The map function relates a sequence to another"
|
||||
(= [__ __ __] (map (fn [x] (* 4 x)) [1 2 3]))
|
||||
(= [4 8 12] (map (fn [x] (* 4 x)) [1 2 3]))
|
||||
|
||||
"You may create that mapping"
|
||||
(= [1 4 9 16 25] (map (fn [x] __) [1 2 3 4 5]))
|
||||
(= [1 4 9 16 25] (map (fn [x] (* x x)) [1 2 3 4 5]))
|
||||
|
||||
"Or use the names of existing functions"
|
||||
(= __ (map nil? [:a :b nil :c :d]))
|
||||
(= [false false true false false] (map nil? [:a :b nil :c :d]))
|
||||
|
||||
"A filter can be strong"
|
||||
(= __ (filter (fn [x] false) '(:anything :goes :here)))
|
||||
(= '() (filter (fn [x] false) '(:anything :goes :here)))
|
||||
|
||||
"Or very weak"
|
||||
(= __ (filter (fn [x] true) '(:anything :goes :here)))
|
||||
(= '(:anything :goes :here) (filter (fn [x] true) '(:anything :goes :here)))
|
||||
|
||||
"Or somewhere in between"
|
||||
(= [10 20 30] (filter (fn [x] __) [10 20 30 40 50 60 70 80]))
|
||||
(= [10 20 30] (filter (fn [x] (< x 40)) [10 20 30 40 50 60 70 80]))
|
||||
|
||||
"Maps and filters may be combined"
|
||||
(= [10 20 30] (map (fn [x] __) (filter (fn [x] __) [1 2 3 4 5 6 7 8])))
|
||||
(= [10 20 30] (map (fn [x] (* 10 x)) (filter (fn [x] (< x 4)) [1 2 3 4 5 6 7 8])))
|
||||
|
||||
"Reducing can increase the result"
|
||||
(= __ (reduce (fn [a b] (* a b)) [1 2 3 4]))
|
||||
(= 24 (reduce (fn [a b] (* a b)) [1 2 3 4]))
|
||||
|
||||
"You can start somewhere else"
|
||||
(= 2400 (reduce (fn [a b] (* a b)) __ [1 2 3 4]))
|
||||
(= 2400 (reduce (fn [a b] (* a b)) 100 [1 2 3 4]))
|
||||
|
||||
"Numbers are not the only things one can reduce"
|
||||
(= "longest" (reduce (fn [a b]
|
||||
(if (< __ __) b a))
|
||||
(if (< (.length a) (.length b)) b a))
|
||||
["which" "word" "is" "longest"])))
|
||||
|
|
|
|||
Loading…
Reference in a new issue