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Quick check of iOS function 
1. Gauss function, rounded down to floor (1.0/4)=0; floor（4.0/4）＝1; floor（5.0/4）＝1; floor（8.0/4）＝2; The floor () method is to round down, similar to the Gauss function [] in mathematics. It can obtain the maximum integer not greater than the floating point number