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[walker] Supply ancestors to visitor functions

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Peter Rust 2014-02-25 13:03:55 -08:00 committed by Marijn Haverbeke
parent 5bd50cce6f
commit 954ddac8b9
2 changed files with 21 additions and 0 deletions
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4
README.md
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@ -155,6 +155,10 @@ simply visit all statements and expressions and not produce a
meaningful state. (An example of a use of state it to track scope at meaningful state. (An example of a use of state it to track scope at
each point in the tree.) each point in the tree.)
**ancestor**`(node, visitors, base, state)` does a 'simple' walk over
a tree, building up an array of ancestor nodes (including the current node)
and passing the array to callbacks in the `state` parameter.
**recursive**`(node, state, functions, base)` does a 'recursive' **recursive**`(node, state, functions, base)` does a 'recursive'
walk, where the walker functions are responsible for continuing the walk, where the walker functions are responsible for continuing the
walk on the child nodes of their target node. `state` is the start walk on the child nodes of their target node. `state` is the start

17
util/walk.js
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@ -32,6 +32,23 @@
c(node, state); c(node, state);
}; };
// An ancestor walk builds up an array of ancestor nodes (including
// the current node) and passes them to the callback as the state parameter.
exports.ancestor = function(node, visitors, base, state) {
if (!base) base = exports.base;
if (!state) state = [];
function c(node, st, override) {
var type = override || node.type, found = visitors[type];
if (node != st[st.length - 1]) {
st = st.slice();
st.push(node);
}
base[type](node, st, c);
if (found) found(node, st);
}
c(node, state);
};
// A recursive walk is one where your functions override the default // A recursive walk is one where your functions override the default
// walkers. They can modify and replace the state parameter that's // walkers. They can modify and replace the state parameter that's
// threaded through the walk, and can opt how and whether to walk // threaded through the walk, and can opt how and whether to walk