sequence function: catalytic-reaction

    description:
        catalytic-reaction(sp, sp, sp)
        process a catalyzed reaction (that doesn't consume the reactants) 
        if the necessary reactants are not present, then the state is left unchanged.
      
        catalytic-reaction(input-sp, |a> + |b>, |c> +|d>)
        is equivalent to:
            input-sp + |c> + |d>
        provided |a> + |b> is in input-sp
        else, return input-sp

        an alternate definition:
        catalytic-reaction (*,*,*) #=> if(is-subset(|_self2>, |_self1>), |_self1> + |_self3>, |_self1>)

    examples:
        
    
    see also:
        consume-reaction