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Merge pull request #5812 from roc-lang/dec-range-docs

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Clarify Dec range and decimal places in docs
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Brendan Hansknecht 2023-09-16 10:43:51 +00:00 • committed by GitHub
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crates/compiler/builtins/roc/Num.roc
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@ -348,8 +348,8 @@ Int range : Num (Integer range)
##
## Roc fractions come in two flavors: fixed-point base-10 and floating-point base-2.
##
## * [Dec] is a 128-bit [fixed-point](https://en.wikipedia.org/wiki/Fixed-point_arithmetic) base-10 number. It's a great default choice, especially when precision is important - for example when representing currency. With [Dec], 0.1 + 0.2 returns 0.3.
## * [F64] and [F32] are [floating-point](https://en.wikipedia.org/wiki/Floating-point_arithmetic) base-2 numbers. They sacrifice precision for lower memory usage and improved performance on some operations. This makes them a good fit for representing graphical coordinates. With [F64], 0.1 + 0.2 returns 0.3000000000000000444089209850062616169452667236328125.
## * [Dec] is a 128-bit [fixed-point](https://en.wikipedia.org/wiki/Fixed-point_arithmetic) base-10 number. It's a great default choice, especially when precision is important - for example when representing currency. With [Dec], `0.1 + 0.2` returns `0.3`. [Dec] has 18 decimal places of precision and a range from `-170_141_183_460_469_231_731.687303715884105728` to `170_141_183_460_469_231_731.687303715884105727`.
## * [F64] and [F32] are [floating-point](https://en.wikipedia.org/wiki/Floating-point_arithmetic) base-2 numbers. They sacrifice precision for lower memory usage and improved performance on some operations. This makes them a good fit for representing graphical coordinates. With [F64], `0.1 + 0.2` returns `0.30000000000000004`.
##
## If you don't specify a type, Roc will default to using [Dec] because it's
## the least error-prone overall. For example, suppose you write this: