Residual operators are used when "material implication" is involved.
right residual : a (r\s) b ⇔ ∀x:x r a→x s b . In other words: (a,b) is in the right residual of r and s means that for every x, pair (x,a) is in relation r implies that pair (x,b) is in s.
left residual : . In words: is in the left residual of and
means that for every pair is in relation implies that pair is in .
diamond: . In words: For every , both and are true or both are false.
shows how you can type boolean (and other) operators in your Ampersand script.
Would you like a different explanation of the residual operators? explains them in natural language. for visualized examples about residual operators.