How to put some values from a list into a function in a Do loop

Question

I want to program a code in MATHEMATICA in order to calculate some values in different iteration. For example, assume this list:

list={1,2,3,4,5}

Now assume that the function is :

f1=Function[u,3+u][x]

I want to use a Do loop to orderly put each integer from the list into f1 function and Do loop uses 5 iteration ({i,1,5}) and gives 5 answers using the values in the list. For this example, The results will be :

4 5 6 7 8

I wonder if anyone could help me with this problem.

Answer 1

I think you want to define f1 as

f1 = Function[u, 3 + u]

since the form you started with would have created the function and then applied it to x.

The easiest way to do what you want is to use Map:

Map[f1, list]

which has an equivalent syntax

f1 /@ list

If you really must use a Do loop, you would do it as follows:

Module[{result = {}}, Do[AppendTo[result, f1[i]], {i, list}]; result]

This is a lot more work. The Module that wraps the Do loop creates a result symbol to hold your output. The Do loop iterates over the elements of list, appending the computation of f1 on each element to the result output.