[[discuss tcl variable ''type'' of int - how much data fits in that amount, when does tcl use it, when does it benefit the user, etc.]]

The [expr]-function int returns the part of a number that fits in the native [C] ''long'' integer type. For non-integers, this means the decimals are discarded (truncation). For numbers of large absolute value, the most significant bits are discarded, but how many are kept depends on details in how Tcl was compiled. [tcl_platform](wordSize) gives the size in ''bytes'' of the native ''long'' type.

 % set tcl_platform(wordSize)
 4
 % expr int(2.3e7)
 23000000
 % expr int(2.3e8)
 230000000
 % expr int(2.3e9)
 -1994967296
 % expr int(0x70102030*2)
 -534757280
 % expr 70000*70000
 4900000000
 % expr int(70000*70000)
 605032704

Note that you can have
 % expr int(1e30)
 0

For "making an integer out of a real number", one should generally use [round] rather than [int], because int(0.999999999) is very different from int(1.00000001). An exception to this rule of thumb is on the output of [rand], where
  expr {1 + int(rand()*6)}
is really the way to "roll a dice". This is in part because the value of [rand] is really an integer that masquerades as a number >0 and <1.

[int] has two companions for larger integers:
   * [wide] for 64-bit integers (Tcl8.4+)
   * [entier] (French pronounciation) for unlimited size integers (Tcl8.5+)
All of these do truncation when applied to doubles. For more controlled conversion to integers there are:
   * [round] for proper rounding.
   * [floor] for rounding downwards. ''Returns a [double] in type, although the value has zero fractional part.''
   * [ceil] for rounding upwards. ''Returns a [double] in type, although the value has zero fractional part.''
For going the other way there is:
   * [double] converts a number to double-precision floating-point form.

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%| [Category Function] | [Category Glossary] |%
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