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fold_pair

p3_binary_pcs

Function fold_pair 

Source 
pub fn fold_pair<F, EF>(index: usize, beta: EF, lo: F, hi: F) -> EF
where
    F: TowerLevel,
    EF: ExtensionField<F>,
Expand description

Fold one pair of the codeword.

lo is the symbol at domain_point(2 * index), hi the one at domain_point(2 * index + 1).

The two symbols come from the codeword’s own alphabet, the challenge from the wider field. The novel-basis halves are formed in the narrow alphabet, and only the last step widens.