tmp/tmpp3guq0g7/{from.md → to.md}
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### Constant evaluation context <a id="meta.const.eval">[[meta.const.eval]]</a>
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``` cpp
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constexpr bool is_constant_evaluated() noexcept;
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```
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*Returns:* `true` if and only if evaluation of the call occurs within
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the evaluation of an expression or conversion that is manifestly
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constant-evaluated [[expr.const]].
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[*Example 1*:
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``` cpp
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constexpr void f(unsigned char *p, int n) {
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if (std::is_constant_evaluated()) { // should not be a constexpr if statement
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for (int k = 0; k<n; ++k) p[k] = 0;
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} else {
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memset(p, 0, n); // not a core constant expression
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}
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}
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```
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— *end example*]
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