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fixing isList fo the negative case. Oops.

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This commit is contained in:
Danny Yoo 2012-02-16 23:44:42 -05:00
parent faf04792a2
commit 4cf6865862
1 changed files with 18 additions and 7 deletions
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25
js-assembler/runtime-src/baselib-lists.js
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@ -266,25 +266,36 @@
if (hare === EMPTY) {
return true;
}
if (!(hare instanceof Cons)) { return false; }
while (true) {
if (!(hare instanceof Cons)) { return false; }
if (tortoise instanceof Cons) {
tortoise = tortoise.rest;
}
// Loop invariant: at the beginning of the loop, both tortoise
// and hare should be pointing to a cons cell.
tortoise = tortoise.rest;
hare = hare.rest;
if (hare instanceof Cons) {
// optimization to get amortized linear time isList:
if (hare._isList) { tortoise._isList = true; return true; }
if (hare._isList !== undefined) {
tortoise._isList = hare._isList; return hare._isList;
}
hare = hare.rest;
// optimization to get amortized linear time isList:
if (hare instanceof Cons && hare._isList) { tortoise._isList = true; return true; }
if (hare instanceof Cons && hare._isList !== undefined) {
tortoise._isList = hare._isList; return hare._isList;
}
}
if (hare === EMPTY) {
// optimization to get amortized linear time isList:
tortoise._isList = true;
return true;
}
if (tortoise === hare) { return false; }
if (tortoise === hare) {
tortoise._isList = false;
return false;
}
if (!(hare instanceof Cons)) {
tortoise._isList = false;
return false;
}
}
};