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Ruby Programming
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VALUE as an Immediate Object

As we said above, immediate values are not pointers: Fixnum, Symbol, true, false, and nil are stored directly in VALUE.

Fixnum values are stored as 31-bit numbers[Or 63-bit on wider CPU architectures.] that are formed by shifting the original number left 1 bit and then setting the least significant bit (bit 0) to ``1.'' When VALUE is used as a pointer to a specific Ruby structure, it is guaranteed always to have an LSB of zero; the other immediate values also have LSBs of zero. Thus, a simple bit test can tell you whether or not you have a Fixnum.

There are several useful conversion macros for numbers as well as other standard datatypes shown in Table 17.1 on page 174.

The other immediate values (true, false, and nil) are represented in C as the constants Qtrue, Qfalse, and Qnil, respectively. You can test VALUE variables against these constants directly, or use the conversion macros (which perform the proper casting).
Ruby Programming
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