tput"><div><div class="alectryon-messages"><blockquote class="alectryon-message"><span class="kd">structure</span> iff : <span class="kt">Prop</span> <span class="bp">‚Üí</span> <span class="kt">Prop</span> <span class="bp">‚Üí</span> <span class="kt">Prop</span>
fields:
iff.mp : <span class="bp">‚àÄ</span> {a b : <span class="kt">Prop</span>}, (a <span class="bp">‚Üî</span> b) <span class="bp">‚Üí</span> a <span class="bp">‚Üí</span> b
iff.mpr : <span class="bp">‚àÄ</span> {a b 