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15 lines
800 B
Text
15 lines
800 B
Text
constant::defer creates a subroutine which on the first call runs given code to
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calculate its value, and on any subsequent calls just returns that value, like a
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constant. The value code is discarded once run, allowing it to be garbage
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collected.
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Deferring a calculation is good if it might take a lot of work or produce a big
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result but is only needed sometimes or only well into a program run. If it's
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never needed then the value code never runs.
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A deferred constant is generally not inlined or folded (see "Constant Folding"
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in perlop) since it's not a single scalar value. In the current implementation a
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deferred constant becomes a plain constant after the first use, so may inline
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etc in code compiled after that (see "IMPLEMENTATION" below).
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WWW: https://metacpan.org/release/constant-defer
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