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Merge branch 'op2'; placeholder-y semantics for op
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@buzzdecafe
buzzdecafe committed Sep 28, 2014
2 parents 7d67b46 + eb6844a commit a234239
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92 changes: 57 additions & 35 deletions ramda.js
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Expand Up @@ -229,23 +229,23 @@
};
}

var _; // This is intentionally left `undefined`.
var __; // This is intentionally left `undefined`.
try {
Object.defineProperty(R, '_', {writable: false, value: _});
Object.defineProperty(R, '__', {writable: false, value: __});
} catch (e) {
R._ = _;
R.__ = __;
}

/**
* Converts a function into something like an infix operation, meaning that
* when called with a single argument, that argument is applied to the
* second position, sort of a curry-right. This allows for more natural
* processing of functions which are really binary operators.
* Uses a placeholder to convert a binary function into something like an infix operation.
* When called with an `undefined` placeholder (e.g. `R.__`) the second argument is applied to the
* second position, and it returns a function waiting for its first argument.
* This can allow for more natural processing of functions which are really binary operators.
*
* @func
* @memberOf R
* @category Functions
* @param {function} fn The operation to adjust
* @param {function} fn The binary operation to adjust
* @return {function} A new function that acts somewhat like an infix operator.
* @example
*
Expand All @@ -254,20 +254,28 @@
* });
*
* div(6, 3); //=> 2
* div(6, _)(3); //=> 2 // note: `_` here is just an `undefined` value. You could use `void 0` instead
* div(3)(6); //=> 2
* div(6)(3); //=> 2
* div(__, 3)(6); //=> 2 // note: `__` here is just an `undefined` value. You could use `void 0` instead
* div(__)(3, 6); //=> 2
* div(__)(3)(6); //=> 2
*/
var op = R.op = function op(fn) {
var length = fn.length;
if (length < 2) {throw new Error('Expected binary function.');}
var left = curry(fn), right = curry(R.flip(fn));
if (length !== 2) {throw new Error('Expected binary function.');}

return function(a, b) {
return function _op(a, b) {
switch (arguments.length) {
case 0: throw noArgsException();
case 1: return right(a);
case 2: return (b === R._) ? left(a) : left.apply(null, arguments);
default: return left.apply(null, arguments);
case 1:
if (a === __) {
return R.flip(_op);
}
return R.lPartial(fn, a);
default:
if (a === __) {
return R.rPartial(fn, b);
}
return fn(a, b);
}
};
};
Expand Down Expand Up @@ -4284,16 +4292,17 @@
* @param {number} a The first value.
* @param {number} b The second value.
* @return {number} The result of `a - b`.
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.subtract(10, 8); //=> 2
*
* var minus5 = R.subtract(5);
* var minus5 = R.subtract(__, 5); // '__' stands for any `undefined` value
* minus5(17); //=> 12
*
* // note: In this example, `_` is just an `undefined` value. You could use `void 0` instead
* var complementaryAngle = R.subtract(90, _);
* var complementaryAngle = R.subtract(90);
* complementaryAngle(30); //=> 60
* complementaryAngle(72); //=> 18
*/
Expand All @@ -4302,8 +4311,6 @@

/**
* Divides two numbers. Equivalent to `a / b`.
* While at times the curried version of `divide` might be useful,
* probably the curried version of `divideBy` will be more useful.
*
* @func
* @memberOf R
Expand All @@ -4312,16 +4319,17 @@
* @param {number} a The first value.
* @param {number} b The second value.
* @return {number} The result of `a / b`.
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.divide(71, 100); //=> 0.71
*
* // note: In this example, `_` is just an `undefined` value. You could use `void 0` instead
* var half = R.divide(2);
* // note: In this example, `__` is just an `undefined` value. You could use `void 0` instead
* var half = R.divide(__, 2);
* half(42); //=> 21
*
* var reciprocal = R.divide(1, _);
* var reciprocal = R.divide(1);
* reciprocal(4); //=> 0.25
*/
R.divide = op(function _divide(a, b) { return a / b; });
Expand All @@ -4339,7 +4347,8 @@
* @param {number} a The value to the divide.
* @param {number} b The pseudo-modulus
* @return {number} The result of `b % a`.
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @see R.mathMod
* @example
*
Expand All @@ -4348,7 +4357,7 @@
* R.modulo(-17, 3); //=> -2
* R.modulo(17, -3); //=> 2
*
* var isOdd = R.modulo(2);
* var isOdd = R.modulo(__, 2);
* isOdd(42); //=> 0
* isOdd(21); //=> 1
*/
Expand Down Expand Up @@ -4383,6 +4392,8 @@
* @param {number} p the modulus.
* @return {number} The result of `b mod a`.
* @see R.moduloBy
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.mathMod(-17, 5); //=> 3
Expand All @@ -4392,12 +4403,12 @@
* R.mathMod(17.2, 5); //=> NaN
* R.mathMod(17, 5.3); //=> NaN
*
* var clock = R.mathMod(12);
* var clock = R.mathMod(__, 12);
* clock(15); //=> 3
* clock(24); //=> 0
*
* // note: In this example, `_` is just an `undefined` value. You could use `void 0` instead
* var seventeenMod = R.mathMod(17, _);
* var seventeenMod = R.mathMod(17);
* seventeenMod(3); //=> 2
* seventeenMod(4); //=> 1
* seventeenMod(10); //=> 7
Expand All @@ -4409,7 +4420,6 @@
});



/**
* Adds together all the elements of a list.
*
Expand Down Expand Up @@ -4454,14 +4464,15 @@
* @param {Number} a
* @param {Number} b
* @return {Boolean} a < b
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.lt(2, 6); //=> true
* R.lt(2, 0); //=> false
* R.lt(2, 2); //=> false
* R.lt(5)(10); //=> false // default currying is right-sectioned
* R.lt(5, _)(10); //=> true // left-sectioned currying
* R.lt(5)(10); //=> true
* R.lt(__, 5)(10); //=> false // right-sectioned currying
*/
R.lt = op(function _lt(a, b) { return a < b; });

Expand All @@ -4476,12 +4487,16 @@
* @param {Number} a
* @param {Number} b
* @return {Boolean} a <= b
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.lte(2, 6); //=> true
* R.lte(2, 0); //=> false
* R.lte(2, 2); //=> true
* R.lte(__, 2)(1); //=> true
* R.lte(2)(10); //=> true
* R.lte(__)(5, 4) // => true
*/
R.lte = op(function _lte(a, b) { return a <= b; });

Expand All @@ -4496,12 +4511,16 @@
* @param {Number} a
* @param {Number} b
* @return {Boolean} a > b
* @note Operator: this is right-curried by default, but can be called via sections
* @note Operator: Since this is a non-commutative infix operator converted to prefix, it can
* be curried right by explicitly passing `undefined` for its first argument.
* @example
*
* R.gt(2, 6); //=> false
* R.gt(2, 0); //=> true
* R.gt(2, 2); //=> false
* R.gt(__, 2)(10); //=> true
* R.gt(2)(10); //=> false
* R.lte(__)(4, 5) // => true
*/
R.gt = op(function _gt(a, b) { return a > b; });

Expand All @@ -4522,6 +4541,9 @@
* R.gte(2, 6); //=> false
* R.gte(2, 0); //=> true
* R.gte(2, 2); //=> true
* R.gte(__, 6)(2); //=> false
* R.gte(2)(0); //=> true
* R.gte(__)(1, 2); //=> true
*/
R.gte = op(function _gte(a, b) { return a >= b; });

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