W𝑊{W}F(X,X)𝐹𝑋𝑋{F(X,X)}F(Y,Y)𝐹𝑌𝑌{F(Y,Y)}F(X,Y)𝐹𝑋𝑌{F(X,Y)}wXsubscript𝑤𝑋\scriptstyle{w_{X}}wYsubscript𝑤𝑌\scriptstyle{w_{Y}}F(mathrmidifx..⋄lsei,f)\scriptstyle{F(mathrm{id}{ifx..lse\par i},f)}F(f,mathrmidifx..⋄lsei)\scriptstyle{F(f,mathrm{id}{ifx..lse\par i})}