NOT_CONV : conv
NOT_CONV "~F" = |- ~F = T NOT_CONV "~T" = |- ~T = F NOT_CONV "~~t" = |- ~~t = t
#NOT_CONV "~~~~T";; |- ~~~~T = ~~T #NOT_CONV "~~T";; |- ~~T = T #NOT_CONV "~T";; |- ~T = F