[R] difference between "external pointer" and "weak reference"

[Vanguelov, Krassimir]

Dear R-help,

Could you tell me where can I read more about the difference between
"external pointer"(EXTPTRSXP) and "weak reference"(WEAKREFSXP) in R and what
were they intended for? 

Regards,

Krassimir Vanguelov 


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