Functional Programming in R by Thomas Mailund

Author:Thomas Mailund
Language: eng
Format: epub, pdf
Publisher: Apress, Berkeley, CA

When we evaluate the expression inside the function, 2 * x, R goes searching for "x and finds it in the first environment. It sees that it is referring to a call, so to get a value it needs to evaluate this call. Because the call has its own environment chain, it will use this chain to evaluate the expression. So evaluating the call 2 * x it uses this chain:

["f -> function(x) 2 * x, "x -> 4]

Here it finds that the variable name "x is mapped to 4, so it evaluates 3 * 4 and we get the value 12 back. This is then inserted into the environment for the function call so future evaluations will refer to the value and not the call expression:

["x -> 12] -> ["f -> function(x) 2 * x, "x -> 4]

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