expGen += genExp(((Binexp) e).l) + "sw $a0 0($sp)\n"
                                + "addiu $sp $sp -4 \n"
                                + genExp(((Binexp) e).r)
                                + "lw $t1 4($sp) \n" + "sub $a0 $t1 $a0 \n"
                                + "addiu $sp $sp 4 \n";