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regexp: add S.replace #693

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merged 1 commit into from Aug 24, 2020
Merged

regexp: add S.replace #693

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6 changes: 3 additions & 3 deletions .circleci/config.yml
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Expand Up @@ -28,7 +28,7 @@ jobs:
nvm exec $1 npm test
}
case $CIRCLE_NODE_INDEX in
0) test_with_version 8 ;;
1) test_with_version 10 ;;
2) npm install && npm test ;;
0) test_with_version 10 ;;
1) npm install && npm test ;;
2) test_with_version 14 ;;
esac
47 changes: 47 additions & 0 deletions index.js
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Expand Up @@ -4403,6 +4403,53 @@
impl: matchAll
};

//# replace :: (Array (Maybe String) -> String) -> RegExp -> String -> String
//.
//. Replaces occurrences of the given pattern within the given string
//. in accordance with the given replacement function, which receives an
//. array of captured values. Replaces all occurrences of the pattern if
//. its `g` flag is set; just the first occurrence otherwise.
//.
//. ```javascript
//. > S.replace (([$1]) => S.maybe ('') (S.toUpper) ($1)) (/(\w)/) ('foo')
//. 'Foo'
//.
//. > S.replace (([$1]) => S.maybe ('') (S.toUpper) ($1)) (/(\w)/g) ('foo')
//. 'FOO'
//.
//. > S.replace (S.show) (/(foo)(bar)?/) ('<>')
//. '<>'
//.
//. > S.replace (S.show) (/(foo)(bar)?/) ('<foo>')
//. '<[Just ("foo"), Nothing]>'
//.
//. > S.replace (S.show) (/(foo)(bar)?/) ('<foobar>')
//. '<[Just ("foo"), Just ("bar")]>'
//. ```
function replace(substitute) {
return function(pattern) {
return function(text) {
return text.replace (pattern, function() {
var groups = [];
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Is it possible to know the length of this array upfront? Say, using var groups = new Array(arguments.length). If so, then that would get you slightly better performance at relatively low implementation and maintenance cost. You would have to alter groups.push statements to index assignment statements instead, eg: groups[idx] = (...).

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Is it possible to know the length of this array upfront?

No, due to the existence of named capturing groups:

> '@sanctuary-js'.replace (/@([-\w]+)/, function() { return arguments.length; })
'4'

> '@sanctuary-js'.replace (/@(?<username>[-\w]+)/, function() { return arguments.length; })
'5'

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Ah, so these named groups are skipped? Is that what the typeof check below is doing?

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That's right. I imagine groups is omitted when the pattern contains no named capturing groups to preserve backward compatibility. Providing the sensible empty value, {}, as an additional argument would break programs that assume that Array.prototype.slice.call(arguments, 1, -2) extracts (only) the captured values.

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Oh, wow. It took me a really long time to realize that what's happening there is: skip one argument, and keep taking arguments until a number is encountered. The numeric argument signifies the "end" of the capture group arguments. Wow. The signature of JavaScript's replace is crazier than I remember.

var group, idx = 1;
// eslint-disable-next-line no-plusplus
while (typeof (group = arguments[idx++]) !== 'number') {
groups.push (group == null ? Nothing : Just (group));
}
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return substitute (groups);
});
};
};
}
_.replace = {
consts: {},
types: [$.Fn ($.Array ($.Maybe ($.String))) ($.String),
$.RegExp,
$.String,
$.String],
impl: replace
};

//. ### String

//# toUpper :: String -> String
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2 changes: 2 additions & 0 deletions test/.eslintrc.json
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@@ -1,9 +1,11 @@
{
"root": true,
"extends": ["../node_modules/sanctuary-style/eslint-es6.json"],
"parserOptions": {"ecmaVersion": 2018},
"env": {"node": true},
"globals": {"suite": false, "test": false},
"rules": {
"comma-dangle": ["error", {"arrays": "always-multiline", "objects": "always-multiline", "functions": "never"}],
"max-len": ["off"]
}
}
19 changes: 19 additions & 0 deletions test/replace.js
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@@ -0,0 +1,19 @@
'use strict';

const S = require ('..');

const eq = require ('./internal/eq');


test ('replace', () => {

eq (S.show (S.replace)) ('replace :: (Array (Maybe String) -> String) -> RegExp -> String -> String');

eq (S.replace (([$1]) => S.maybe ('') (S.toUpper) ($1)) (/(\w)/) ('foo')) ('Foo');
eq (S.replace (([$1]) => S.maybe ('') (S.toUpper) ($1)) (/(\w)/g) ('foo')) ('FOO');
eq (S.replace (S.show) (/(foo)(bar)?/) ('<>')) ('<>');
eq (S.replace (S.show) (/(foo)(bar)?/) ('<foo>')) ('<[Just ("foo"), Nothing]>');
eq (S.replace (S.show) (/(foo)(bar)?/) ('<foobar>')) ('<[Just ("foo"), Just ("bar")]>');
eq (S.replace (S.show) (/@(?<username>[-\w]+)/) ('@sanctuary-js')) ('[Just ("sanctuary-js")]');

});