vector::reserve() with value less than current size().

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  • jason.cipriani@gmail.com
    #1

    vector::reserve() with value less than current size().

    What is the official word on what happens if I call reserve() on an
    std::vector, and specify a capacity that is less than the current
    *size* (not capacity) of that vector? Is it supposed to resize() the
    vector as well? Or just not modify anything?

    Thanks,
    Jason
    Tags: None
    • Joe Gottman
      #2
      Re: vector::reserve () with value less than current size().

      jason.cipriani@ gmail.com wrote:
      What is the official word on what happens if I call reserve() on an
      std::vector, and specify a capacity that is less than the current
      *size* (not capacity) of that vector? Is it supposed to resize() the
      vector as well? Or just not modify anything?
      >
      Thanks,
      Jason
      reserve() never reduces capacity; it just increases it. Therefore this
      is a no-op.

      Joe Gottman

        Comment

        • Salt_Peter
          #3
          Re: vector::reserve () with value less than current size().

          On Nov 18, 8:25 pm, "jason.cipri... @gmail.com"
          <jason.cipri... @gmail.comwrote :
          What is the official word on what happens if I call reserve() on an
          std::vector, and specify a capacity that is less than the current
          *size* (not capacity) of that vector? Is it supposed to resize() the
          vector as well? Or just not modify anything?
          >
          Thanks,
          Jason
          The size of the vector is irrelevant. If reserve's arguement is less
          than or equal to its capacity, nothing happens. Swap the vector to
          (maybe) change its capacity.

            Comment

            • jason.cipriani@gmail.com
              #4
              Re: vector::reserve () with value less than current size().

              On Nov 18, 8:48 pm, Joe Gottman <jgott...@carol ina.rr.comwrote :
              jason.cipri...@ gmail.com wrote:
              What is the official word on what happens if I call reserve() on an
              std::vector, and specify a capacity that is less than the current
              *size* (not capacity) of that vector? Is it supposed to resize() the
              vector as well? Or just not modify anything?
              >
              Thanks,
              Jason
              >
              reserve() never reduces capacity; it just increases it.  Therefore this
              is a no-op.
              That's what I was looking for, thanks Joe and Salt_Peter.

              Also, sorry, I'm looking now and it turns out that actually *is*
              stated in the docs I was reading, it's just in a footnote that I
              missed. :-o

              Jason

                Comment

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