#python #scip
A name evaluates to the value associated with that name in the current
environment.
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Open its to the
point where we need to evaluate, not call expressions, but primitive expressions
such as numerals (e.g., 2) and names (e.g., add ). We take care of the
primitive cases by stipulating that
A numeral evaluates to the number it names, <span>A name evaluates to the value associated with that name in the current
environment.
Notice the important role of an environment in determining the meaning of the
symbols in expressions<span><body><html>Original toplevel document
1.2 Elements of Programmingrule
is applied, and the result of that expression. Viewing evaluation in terms of
this tree, we can imagine that the values of the operands percolate upward,
starting from the terminal nodes and then combining at higher and higher
levels.
<span>Next, observe that the repeated application of the first step brings us to the
point where we need to evaluate, not call expressions, but primitive expressions
such as numerals (e.g., 2) and names (e.g., add ). We take care of the
primitive cases by stipulating that
A numeral evaluates to the number it names, A name evaluates to the value associated with that name in the current
environment.
Notice the important role of an environment in determining the meaning of the
symbols in expressions. In Python, it is meaningless to speak of the value of an
expression such as
>>> add(x, 1)
without specifying any information about the environment that would provide a
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