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| -rw-r--r-- | git.html.markdown | 4 | ||||
| -rw-r--r-- | jsonnet.html.markdown | 139 | ||||
| -rw-r--r-- | matlab.html.markdown | 2 | ||||
| -rw-r--r-- | nl-nl/json-nl.html.markdown | 13 | ||||
| -rw-r--r-- | rst.html.markdown | 6 | ||||
| -rw-r--r-- | set-theory.html.markdown | 162 | ||||
| -rw-r--r-- | smalltalk.html.markdown | 2 |
7 files changed, 316 insertions, 12 deletions
diff --git a/git.html.markdown b/git.html.markdown index aa96c90a..a40ef01b 100644 --- a/git.html.markdown +++ b/git.html.markdown @@ -82,12 +82,12 @@ pushed to other repositories, or not! ### Branch A branch is essentially a pointer to the last commit you made. As you go on -committing, this pointer will automatically update to point the latest commit. +committing, this pointer will automatically update to point to the latest commit. ### Tag A tag is a mark on specific point in history. Typically people use this -functionality to mark release points (v1.0, and so on) +functionality to mark release points (v1.0, and so on). ### HEAD and head (component of .git dir) diff --git a/jsonnet.html.markdown b/jsonnet.html.markdown new file mode 100644 index 00000000..175642d4 --- /dev/null +++ b/jsonnet.html.markdown @@ -0,0 +1,139 @@ +--- +language: jsonnet +filename: learnjsonnet.jsonnet +contributors: + - ["Huan Wang", "https://github.com/fredwangwang"] +--- + +Jsonnet is a powerful templating language for JSON. Any valid JSON +document is a valid Jsonnet object. For an interactive demo/tutorial, +click [here](https://jsonnet.org/learning/tutorial.html) + +```python +// single line comment + +/* + multiline comment +*/ + +// as well as python style comment + +# define a variable. +# Variables have no effect in the generated JSON without being used. +local num1 = 1; +local num2 = 1 + 1; +local num3 = 5 - 2; +local num4 = 9 % 5; +local num5 = 10 / 2.0; +# jsonnet is a lazy language, if a variable is not used, it is not evaluated. +local num_runtime_error = 1 / 0; + +# fields are valid identifiers without quotes +local obj1 = { a: 'letter a', B: 'letter B' }; + +local arr1 = ['a', 'b', 'c']; + +# string literals use " or '. +local str1 = 'a' + 'B'; +# multiline text literal in between ||| +# Each line must start with a white space. +local str_multiline = ||| + this is a + multiline string +|||; +# Python-compatible string formatting is available via % +# When combined with ||| this can be used for templating text files. +local str_templating = ||| + %(f1)0.3f +||| % { f1: 1.2345678 }; +assert str_templating == '1.235\n'; + +# if b then e else e. The else branch is optional and defaults to null +local var1 = if 3 < 2 then "YES"; +assert var1 == null; + +local obj2 = { + # variable defined inside the object ends with ',' + local var_in_obj = 0, + + local vowels = ['a', 'e', 'i', 'o', 'u'], + local numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], + + # [num] to look up an array element + first_vowel: vowels[0], + # can also slice the array like in Python + even_numbers: numbers[1::2], + + # python-style list and object comprehensions are also supported + double_numbers: [x * 2 for x in numbers], + even_numbers_map: { + # [ ] syntax in field name is to compute the field name dynamically + [x + '_is_even']: true for x in numbers if x % 2 == 0 + }, + + nested: { + nested_field1: 'some-value', + # self refers to the current object + # ["field-name"] or .field-name can be used to look up a field + nested_field2: self.nested_field1, + nested_field3: self.nested_field1, + # $ refers to outer-most object + nested_field4: $.first_vowel, + + assert self.nested_field1 == self.nested_field2, + assert self.nested_field1 == self.nested_field3, + }, + + special_field: 'EVERYTHING FEELS BAD', +}; + +local obj3 = { + local var_in_obj = 1.234, + local var_in_obj2 = { a: { b: 'c' } }, + + concat_array: [1, 2, 3] + [4], + # strings can be concat with +, + # which implicitly converts one operand to string if needed. + concat_string: '123' + 4, + + # == tests deep equality + equals: { a: { b: 'c', d: {} } } == var_in_obj2, + + special_field: 'this feels good', +}; + +# objects can be merged with + where the right-hand side wins field conflicts +local obj4 = obj2 + obj3; +assert obj4.special_field == 'this feels good'; + +# define a function +# functions have positional parameters, named parameters, and default arguments +local my_function(x, y, z=1) = x + y - z; +local num6 = my_function(7, 8, 9); +local num7 = my_function(8, z=10, y=9); +local num8 = my_function(4, 5); +# inline anonymous function +local num9 = (function(x) x * x)(3); + +local obj5 = { + # define a method + # fields defined with :: are hidden, which does not apper in generated JSON + # function cannot be serialized so need to be hidden + # if the object is used in the generated JSON. + is_odd(x):: x % 2 == 1, +}; +assert obj5 == {}; + +# a jsonnet doucment have to evaluate to something +# be it an object, list, number or just string literal +"FIN" + +``` + +## Further Reading +There are a few but important concepts that are not touched in this exmaple, including: + +- Passing variables from command line: [Parameterize Entire Config](https://jsonnet.org/learning/tutorial.html#parameterize-entire-config) +- Import other jsonnet libraries/files: [Imports](https://jsonnet.org/learning/tutorial.html#imports) +- In depth example of OOP aspect of Jsonnet: [Object-Orientation](https://jsonnet.org/learning/tutorial.html#Object-Orientation) +- Useful standard library: [Stdlib](https://jsonnet.org/ref/stdlib.html) diff --git a/matlab.html.markdown b/matlab.html.markdown index 5790bcc6..4ca31857 100644 --- a/matlab.html.markdown +++ b/matlab.html.markdown @@ -234,7 +234,7 @@ A' % Concise version of complex transpose % On their own, the arithmetic operators act on whole matrices. When preceded % by a period, they act on each element instead. For example: A * B % Matrix multiplication -A .* B % Multiple each element in A by its corresponding element in B +A .* B % Multiply each element in A by its corresponding element in B % There are several pairs of functions, where one acts on each element, and % the other (whose name ends in m) acts on the whole matrix. diff --git a/nl-nl/json-nl.html.markdown b/nl-nl/json-nl.html.markdown index 906112ff..d243802d 100644 --- a/nl-nl/json-nl.html.markdown +++ b/nl-nl/json-nl.html.markdown @@ -5,26 +5,27 @@ contributors: - ["Anna Harren", "https://github.com/iirelu"] - ["Marco Scannadinari", "https://github.com/marcoms"] - ["himanshu", "https://github.com/himanshu81494"] + - ["Maarten Jacobs", "https://github.com/maartenJacobs"] translators: - ["Niels van Velzen", "https://nielsvanvelzen.me"] lang: nl-nl --- -Gezien JSON een zeer eenvouding formaat heeft zal dit een van de simpelste +Gezien JSON een zeer eenvouding formaat heeft zal dit één van de simpelste Learn X in Y Minutes ooit zijn. -JSON heeft volgens de specificaties geen commentaar, ondanks dat hebben de +JSON heeft volgens de specificaties geen commentaar. Ondanks dat hebben de meeste parsers support voor C-stijl (`//`, `/* */`) commentaar. Sommige parsers staan zelfs trailing komma's toe. -(Een komma na het laatste element in een array of ahter de laatste eigenshap van een object). -Het is wel beter om dit soort dingen te vermijden omdat het niet overal zal werken. +(Een komma na het laatste element in een array of achter de laatste eigenschap van een object). +Het is wel beter om dit soort dingen te vermijden omdat het niet in elke parser zal werken. In het voorbeeld zal alleen 100% geldige JSON gebruikt worden. Data types gesupport door JSON zijn: nummers, strings, booleans, arrays, objecten en null. Gesupporte browsers zijn: Firefox(Mozilla) 3.5, Internet Explorer 8, Chrome, Opera 10, Safari 4. -De extensie voor JSON bestanden is ".json". De MIME type is "application/json" -Enkele nadelen van JSON zijn het gebrek een type definities en een manier van DTD. +De extensie voor JSON bestanden is ".json". De MIME type is "application/json". +Enkele nadelen van JSON zijn het gebrek aan type definities en een manier van DTD. ```json { diff --git a/rst.html.markdown b/rst.html.markdown index 2423622e..bdc73c7a 100644 --- a/rst.html.markdown +++ b/rst.html.markdown @@ -49,9 +49,11 @@ Subtitles with dashes You can put text in *italic* or in **bold**, you can "mark" text as code with double backquote ``print()``. +Special characters can be escaped using a backslash, e.g. \\ or \*. + Lists are similar to Markdown, but a little more involved. -Remember to line up list symbols (like - or *) with the left edge of the previous text block, and remember to use blank lines to separate new lists from parent lists: +Remember to line up list symbols (like - or \*) with the left edge of the previous text block, and remember to use blank lines to separate new lists from parent lists: - First item - Second item @@ -86,7 +88,7 @@ There are multiple ways to make links: - By typing a full comprehensible URL : https://github.com/ (will be automatically converted to a link) - By making a more Markdown-like link: `Github <https://github.com/>`_ . -.. _Github https://github.com/ +.. _Github: https://github.com/ ``` diff --git a/set-theory.html.markdown b/set-theory.html.markdown new file mode 100644 index 00000000..c6bc39c5 --- /dev/null +++ b/set-theory.html.markdown @@ -0,0 +1,162 @@ +--- +category: Algorithms & Data Structures +name: Set theory +contributors: +--- +The set theory is a study for sets, their operations, and their properties. It is the basis of the whole mathematical system. + +* A set is a collection of definite distinct items. + +## Basic operators +These operators don't require a lot of text to describe. + +* `∨` means or. +* `∧` means and. +* `,` separates the filters that determine the items in the set. + +## A brief history of the set theory +### Naive set theory +* Cantor invented the naive set theory. +* It has lots of paradoxes and initiated the third mathematical crisis. + +### Axiomatic set theory +* It uses axioms to define the set theory. +* It prevents paradoxes from happening. + +## Built-in sets +* `∅`, the set of no items. +* `N`, the set of all natural numbers. `{0,1,2,3,…}` +* `Z`, the set of all integers. `{…,-2,-1,0,1,2,…}` +* `Q`, the set of all rational numbers. +* `R`, the set of all real numbers. + +### The empty set +* The set containing no items is called the empty set. Representation: `∅` +* The empty set can be described as `∅ = {x|x ≠ x}` +* The empty set is always unique. +* The empty set is the subset of all sets. + +``` +A = {x|x∈N,x < 0} +A = ∅ +∅ = {} (Sometimes) + +|∅| = 0 +|{∅}| = 1 +``` + +## Representing sets +### Enumeration +* List all items of the set, e.g. `A = {a,b,c,d}` +* List some of the items of the set. Ignored items are represented with `…`. E.g. `B = {2,4,6,8,10,…}` + +### Description +* Describes the features of all items in the set. Syntax: `{body|condtion}` + +``` +A = {x|x is a vowel} +B = {x|x ∈ N, x < 10l} +C = {x|x = 2k, k ∈ N} +C = {2x|x ∈ N} +``` + +## Relations between sets +### Belongs to +* If the value `a` is one of the items of the set `A`, `a` belongs to `A`. Representation: `a∈A` +* If the value `a` is not one of the items of the set `A`, `a` does not belong to `A`. Representation: `a∉A` + +### Equals +* If all items in a set are exactly the same to another set, they are equal. Representation: `a=b` +* Items in a set are not order sensitive. `{1,2,3,4}={2,3,1,4}` +* Items in a set are unique. `{1,2,2,3,4,3,4,2}={1,2,3,4}` +* Two sets are equal if and only if all of their items are exactly equal to each other. Representation: `A=B`. Otherwise, they are not equal. Representation: `A≠B`. +* `A=B` if `A ⊆ B` and `B ⊆ A` + +### Belongs to +* If the set A contains an item `x`, `x` belongs to A (`x∈A`). +* Otherwise, `x` does not belong to A (`x∉A`). + +### Subsets +* If all items in a set `B` are items of set `A`, we say that `B` is a subset of `A` (`B⊆A`). +* If B is not a subset of A, the representation is `B⊈A`. + +### Proper subsets +* If `B ⊆ A` and `B ≠ A`, B is a proper subset of A (`B ⊂ A`). Otherwise, B is not a proper subset of A (`B ⊄ A`). + +## Set operations +### Base number +* The number of items in a set is called the base number of that set. Representation: `|A|` +* If the base number of the set is finite, this set is a finite set. +* If the base number of the set is infinite, this set is an infinite set. + +``` +A = {A,B,C} +|A| = 3 +B = {a,{b,c}} +|B| = 2 +|∅| = 0 (it has no items) +``` + +### Powerset +* Let `A` be any set. The set that contains all possible subsets of `A` is called a powerset (written as `P(A)`). + +``` +P(A) = {x|x ⊆ A} + +|A| = N, |P(A)| = 2^N +``` + +## Set operations among two sets +### Union +Given two sets `A` and `B`, the union of the two sets are the items that appear in either `A` or `B`, written as `A ∪ B`. + +``` +A ∪ B = {x|x∈A∨x∈B} +``` + +### Intersection +Given two sets `A` and `B`, the intersection of the two sets are the items that appear in both `A` and `B`, written as `A ∩ B`. + +``` +A ∩ B = {x|x∈A,x∈B} +``` + +### Difference +Given two sets `A` and `B`, the set difference of `A` with `B` is every item in `A` that does not belong to `B`. + +``` +A \ B = {x|x∈A,x∉B} +``` + +### Symmetrical difference +Given two sets `A` and `B`, the symmetrical difference is all items among `A` and `B` that doesn't appear in their intersections. + +``` +A △ B = {x|(x∈A∧x∉B)∨(x∈B∧x∉A)} + +A △ B = (A \ B) ∪ (B \ A) +``` + +### Cartesian product +Given two sets `A` and `B`, the cartesian product between `A` and `B` consists of a set containing all combinations of items of `A` and `B`. + +``` +A × B = { {x, y} | x ∈ A, y ∈ B } +``` + +## "Generalized" operations +### General union +Better known as "flattening" of a set of sets. + +``` +∪A = {x|X∈A,x∈X} +∪A={a,b,c,d,e,f} +∪B={a} +∪C=a∪{c,d} +``` + +### General intersection + +``` +∩ A = A1 ∩ A2 ∩ … ∩ An +``` diff --git a/smalltalk.html.markdown b/smalltalk.html.markdown index d6d369cc..58dccae4 100644 --- a/smalltalk.html.markdown +++ b/smalltalk.html.markdown @@ -388,7 +388,7 @@ y := $A max: $B. ```smalltalk | b x y | x := #Hello. "symbol assignment" -y := 'String', 'Concatenation'. "symbol concatenation (result is string)" +y := #Symbol, #Concatenation. "symbol concatenation (result is string)" b := x isEmpty. "test if symbol is empty" y := x size. "string size" y := x at: 2. "char at location" |