Why use boost :: ice_or instead of || and boost :: ice_and instead of && in enable_if?

Question

As stated in the question, is there a reason why people use the version of the structure over normal conditional expressions?

Answer 1

Excerpt from Acceleration Encoding Recommendation for Integral Constant Expressions :

Do not use logical operators in integral constant expressions; use meta-programming templates instead.

The header contains several workaround patterns that act as logical operators, for example, instead of:

INTEGRAL_CONSTANT1 || INTEGRAL_CONSTANT2

Using:

::boost::type_traits::ice_or<INTEGRAL_CONSTANT1,INTEGRAL_CONSTANT2>::value

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