Why is the “f” required when declaring floats?

Question

Example:

float timeRemaining = 0.58f;

Why is the f is required at the end of this number?

Answer 1

The problem is that .NET, in order to allow some types of implicit operations to be carried out involving float and double, needed to either explicitly specify what should happen in all scenarios involving mixed operands or else allow implicit conversions between the types to be performed in one direction only; Microsoft chose to follow the lead of Java in allowing the direction which occasionally favors precision, but frequently sacrifices correctness and generally creates hassle.

In almost all cases, taking the double value which is closest to a particular numeric quantity and assigning it to a float will yield the float value which is closest to that same quantity. There are a few corner cases, such as the value 9,007,199,791,611,905; the best float representation would be 9,007,200,328,482,816 (which is off by 536,870,911), but casting the best double representation (i.e. 9,007,199,791,611,904) to float yields 9,007,199,254,740,992 (which is off by 536,870,913). In general, though, converting the best double representation of some quantity to float will either yield the best possible float representation, or one of two representations that are essentially equally good.

Note that this desirable behavior applies even at the extremes; for example, the best float representation for the quantity 10^308 matches the float representation achieved by converting the best double representation of that quantity. Likewise, the best float representation of 10^309 matches the float representation achieved by converting the best double representation of that quantity.

Unfortunately, conversions in the direction that doesn't require an explicit cast are seldom anywhere near as accurate. Converting the best float representation of a value to double will seldom yield anything particularly close to the best double representation of that value, and in some cases the result may be off by hundreds of orders of magnitude (e.g. converting the best float representation of 10^40 to double will yield a value that compares greater than the best double representation of 10^300.

Alas, the conversion rules are what they are, so one has to live with using silly typecasts and suffixes when converting values in the "safe" direction, and be careful of implicit typecasts in the dangerous direction which will frequently yield bogus results.