58 lines
1.6 KiB
JavaScript
58 lines
1.6 KiB
JavaScript
var assert = require('./assert');
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var isTypeName = require('./isTypeName');
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var isFunction = require('./isFunction');
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var isMaybe = require('./isMaybe');
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var isIdentity = require('./isIdentity');
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var Any = require('./Any');
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var create = require('./create');
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var Nil = require('./Nil');
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var forbidNewOperator = require('./forbidNewOperator');
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var is = require('./is');
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var getTypeName = require('./getTypeName');
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function getDefaultName(type) {
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return '?' + getTypeName(type);
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}
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function maybe(type, name) {
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if (isMaybe(type) || type === Any || type === Nil) { // makes the combinator idempotent and handle Any, Nil
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return type;
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}
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if (process.env.NODE_ENV !== 'production') {
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assert(isFunction(type), function () { return 'Invalid argument type ' + assert.stringify(type) + ' supplied to maybe(type, [name]) combinator (expected a type)'; });
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assert(isTypeName(name), function () { return 'Invalid argument name ' + assert.stringify(name) + ' supplied to maybe(type, [name]) combinator (expected a string)'; });
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}
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var displayName = name || getDefaultName(type);
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var identity = isIdentity(type);
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function Maybe(value, path) {
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if (process.env.NODE_ENV !== 'production') {
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if (identity) {
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forbidNewOperator(this, Maybe);
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}
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}
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return Nil.is(value) ? value : create(type, value, path);
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}
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Maybe.meta = {
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kind: 'maybe',
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type: type,
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name: name,
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identity: identity
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};
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Maybe.displayName = displayName;
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Maybe.is = function (x) {
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return Nil.is(x) || is(x, type);
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};
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return Maybe;
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}
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maybe.getDefaultName = getDefaultName;
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module.exports = maybe;
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