function relu(){

    return {
        type:'relu',
        evaluate:function(input){
            let result = [];
            for(let row of input){
                let val = row[0];
                if(val >0) result.push([val]);
                else result.push([0]);
            }
            return result;
        },
        inputGradient:function(input){
            let result = [];
            for(let row of input){
                let val = row[0];
                if(val >0) result.push([1]);
                else result.push([0]);
            }
            return result;
        },
    };
}