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Add S.keys, S.values and S.pairs #214

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May 18, 2016
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Add S.keys, S.values and S.pairs #214

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48 changes: 48 additions & 0 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
//.
//. R.map(S.toUpper, S.head(words))
//.
//. Sanctuary is designed to work in Node.js and in ES5-compatible browsers.
//.
//. ## Types
//.
//. Sanctuary uses Haskell-like type signatures to describe the types of
Expand Down Expand Up @@ -2746,6 +2748,52 @@
return filter(is(type), Just(x));
});

//# keys :: StrMap a -> Array String
//.
//. Returns the keys of the given string map, in arbitrary order.
//.
//. ```javascript
//. > S.keys({b: 2, c: 3, a: 1}).sort()
//. ['a', 'b', 'c']
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Let's add .sort() to the input, both to ensure determinism and to reinforce the comment about arbitrary ordering.

//. ```
S.keys =
def('keys',
{},
[$.StrMap(a), $.Array($.String)],
Object.keys);

//# values :: StrMap a -> Array a
//.
//. Returns the values of the given string map, in arbitrary order.
//.
//. ```javascript
//. > S.values({a: 1, c: 3, b: 2}).sort()
//. [1, 2, 3]
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Let's .sort() here too.

//. ```
S.values =
def('values',
{},
[$.StrMap(a), $.Array(a)],
function(strMap) {
return Object.keys(strMap).map(function(key) { return strMap[key]; });
});

//# toPairs :: StrMap a -> Array (Pair String a)
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s/toPairs/pairs/

I'll fix this shortly.

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#226

//.
//. Returns the key–value pairs of the given string map, in arbitrary order.
//.
//. ```javascript
//. > S.pairs({b: 2, a: 1, c: 3}).sort()
//. [['a', 1], ['b', 2], ['c', 3]]
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We should probably .sort() here too, though relying on type coercion feels a little dirty.

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@svozza svozza May 18, 2016 •
edited
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Another way to do this that would be to list the elements in each of the functions' examples in an obviously out of order sequence. That way we don't clutter the docs with things that really aren't related to the functions:

S.keys({a: 1, b: 2, c: 3}) // => [c, b, a]
S.values({a: 1, b: 2, c: 3}) // => [1, 3, 2]
S.toPairs({a: 1, b: 2, c: 3}) //=> [['b', 2], ['a', 1], ['c', 3]]

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The root problem is that we're using an ordered collection for something with no inherent order. When comparing two arrays for equality, order is of course significant. To ensure the doctests pass, we have two options:

  • rely on property enumeration order; or
  • use Array#sort.

Thinking about this again, I believe the best approach is to jumble the keys in the input:

> S.keys({c: 3, a: 1, b: 2}).sort()
['a', 'b', 'c']

> S.values({c: 3, a: 1, b: 2}).sort()
[1, 2, 3]

> S.pairs({c: 3, a: 1, b: 2}).sort()
[['a', 1], ['b', 2], ['c', 3]]

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Of course, I'd forgotten about the doc tests.

⚡

//. ```
S.pairs =
def('pairs',
{},
[$.StrMap(a), $.Array($.Pair($.String, a))],
function(strMap) {
return Object.keys(strMap).map(function(k) { return [k, strMap[k]]; });
});

//. ### Number

//# negate :: ValidNumber -> ValidNumber
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59 changes: 59 additions & 0 deletions test/keys.js
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@@ -0,0 +1,59 @@
'use strict';

var throws = require('assert').throws;

var eq = require('./utils').eq;
var errorEq = require('./utils').errorEq;
var S = require('..');


describe('keys', function() {

it('is a unary function', function() {
eq(typeof S.keys, 'function');
eq(S.keys.length, 1);
});

it('type checks its arguments', function() {
throws(function() { S.keys('xxx'); },
errorEq(TypeError,
'Invalid value\n' +
'\n' +
'keys :: StrMap a -> Array String\n' +
' ^^^^^^^^\n' +
' 1\n' +
'\n' +
'1) "xxx" :: String\n' +
'\n' +
'The value at position 1 is not a member of ‘StrMap a’.\n'));

throws(function() { S.keys({a: '1', b: 2, c: '3'}); },
errorEq(TypeError,
'Type-variable constraint violation\n' +
'\n' +
'keys :: StrMap a -> Array String\n' +
' ^\n' +
' 1\n' +
'\n' +
'1) "1" :: String\n' +
' 2 :: Number, FiniteNumber, NonZeroFiniteNumber, Integer, ValidNumber\n' +
' "3" :: String\n' +
'\n' +
'Since there is no type of which all the above values are members, the type-variable constraint has been violated.\n'));
});

it("returns an array of the given object's own keys", function() {
eq(S.keys({}), []);
eq(S.keys({a: 1, b: 2, c: 3}).sort(), ['a', 'b', 'c']);
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It's worth noting that sorted keys would be useful here. ;)

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I'm not sure how it would have made it any easier to copy and paste this test from Ramda's. ;)

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Let's also test S.keys({}).

});

it('does not include prototype properties', function() {
var proto = {a: 1, b: 2};
var obj = Object.create(proto);
obj.c = 3;
obj.d = 4;

eq(S.keys(obj).sort(), ['c', 'd']);
});

});
63 changes: 63 additions & 0 deletions test/pairs.js
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'use strict';

var throws = require('assert').throws;

var eq = require('./utils').eq;
var errorEq = require('./utils').errorEq;
var S = require('..');


describe('toPairs', function() {

var comparePairsAsc = function(a, b) {
return a[0] < b[0] ? -1 : a[0] > b[0] ? 1 : 0;
};

it('is a unary function', function() {
eq(typeof S.pairs, 'function');
eq(S.pairs.length, 1);
});

it('type checks its arguments', function() {
throws(function() { S.pairs('xxx'); },
errorEq(TypeError,
'Invalid value\n' +
'\n' +
'pairs :: StrMap a -> Array (Pair String a)\n' +
' ^^^^^^^^\n' +
' 1\n' +
'\n' +
'1) "xxx" :: String\n' +
'\n' +
'The value at position 1 is not a member of ‘StrMap a’.\n'));

throws(function() { S.pairs({a: '1', b: 2, c: '3'}); },
errorEq(TypeError,
'Type-variable constraint violation\n' +
'\n' +
'pairs :: StrMap a -> Array (Pair String a)\n' +
' ^\n' +
' 1\n' +
'\n' +
'1) "1" :: String\n' +
' 2 :: Number, FiniteNumber, NonZeroFiniteNumber, Integer, ValidNumber\n' +
' "3" :: String\n' +
'\n' +
'Since there is no type of which all the above values are members, the type-variable constraint has been violated.\n'));
});

it('returns an array with the key value pairs of each property of the object', function() {
eq(S.pairs({}), []);
eq(S.pairs({a: 1, b: 2, c: 3}).sort(comparePairsAsc), [['a', 1], ['b', 2], ['c', 3]]);
});

it('does not include prototype properties', function() {
var proto = {a: 1, b: 2};
var obj = Object.create(proto);
obj.c = 3;
obj.d = 4;

eq(S.pairs(obj).sort(comparePairsAsc), [['c', 3], ['d', 4]]);
});

});
59 changes: 59 additions & 0 deletions test/values.js
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@@ -0,0 +1,59 @@
'use strict';

var throws = require('assert').throws;

var eq = require('./utils').eq;
var errorEq = require('./utils').errorEq;
var S = require('..');


describe('values', function() {

it('is a unary function', function() {
eq(typeof S.values, 'function');
eq(S.values.length, 1);
});

it('type checks its arguments', function() {
throws(function() { S.values('xxx'); },
errorEq(TypeError,
'Invalid value\n' +
'\n' +
'values :: StrMap a -> Array a\n' +
' ^^^^^^^^\n' +
' 1\n' +
'\n' +
'1) "xxx" :: String\n' +
'\n' +
'The value at position 1 is not a member of ‘StrMap a’.\n'));

throws(function() { S.values({a: '1', b: 2, c: '3'}); },
errorEq(TypeError,
'Type-variable constraint violation\n' +
'\n' +
'values :: StrMap a -> Array a\n' +
' ^\n' +
' 1\n' +
'\n' +
'1) "1" :: String\n' +
' 2 :: Number, FiniteNumber, NonZeroFiniteNumber, Integer, ValidNumber\n' +
' "3" :: String\n' +
'\n' +
'Since there is no type of which all the above values are members, the type-variable constraint has been violated.\n'));
});

it("returns an array of the given object's own values", function() {
eq(S.values({}), []);
eq(S.values({a: 1, b: 2, c: 3}).sort(), [1, 2, 3]);
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Let's also test S.values({}).

});

it('does not include prototype values', function() {
var proto = {a: 1, b: 2};
var obj = Object.create(proto);
obj.c = 3;
obj.d = 4;

eq(S.values(obj).sort(), [3, 4]);
});

});