diff options
| -rw-r--r-- | lib/pure/strutils.nim | 165 | ||||
| -rw-r--r-- | web/news.txt | 2 |
2 files changed, 167 insertions, 0 deletions
diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim index 55494a8b5..a5c75b4ec 100644 --- a/lib/pure/strutils.nim +++ b/lib/pure/strutils.nim @@ -14,6 +14,7 @@ ## <backends.html#the-javascript-target>`_. import parseutils +from math import pow, round, floor, log10 {.deadCodeElim: on.} @@ -1541,6 +1542,141 @@ proc formatSize*(bytes: int64, result &= prefixes[matchedIndex] result &= "B" +proc formatEng*(f: BiggestFloat, + precision: range[0..32] = 10, + trim: bool = true, + siPrefix: bool = false, + unit: string = nil, + decimalSep = '.'): string {.noSideEffect.} = + ## Converts a floating point value `f` to a string using engineering notation. + ## + ## Numbers in of the range -1000.0<f<1000.0 will be formatted without an + ## exponent. Numbers outside of this range will be formatted as a + ## significand in the range -1000.0<f<1000.0 and an exponent that will always + ## be an integer multiple of 3, corresponding with the SI prefix scale k, M, + ## G, T etc for numbers with an absolute value greater than 1 and m, μ, n, p + ## etc for numbers with an absolute value less than 1. + ## + ## The default configuration (`trim=true` and `precision=10`) shows the + ## **shortest** form that precisely (up to a maximum of 10 decimal places) + ## displays the value. For example, 4.100000 will be displayed as 4.1 (which + ## is mathematically identical) whereas 4.1000003 will be displayed as + ## 4.1000003. + ## + ## If `trim` is set to true, trailing zeros will be removed; if false, the + ## number of digits specified by `precision` will always be shown. + ## + ## `precision` can be used to set the number of digits to be shown after the + ## decimal point or (if `trim` is true) the maximum number of digits to be + ## shown. + ## + ## .. code-block:: nim + ## + ## formatEng(0, 2, trim=false) == "0.00" + ## formatEng(0, 2) == "0" + ## formatEng(0.053, 0) == "53e-3" + ## formatEng(52731234, 2) == "52.73e6" + ## formatEng(-52731234, 2) == "-52.73e6" + ## + ## If `siPrefix` is set to true, the number will be displayed with the SI + ## prefix corresponding to the exponent. For example 4100 will be displayed + ## as "4.1 k" instead of "4.1e3". Note that `u` is used for micro- in place + ## of the greek letter mu (μ) as per ISO 2955. Numbers with an absolute + ## value outside of the range 1e-18<f<1000e18 (1a<f<1000E) will be displayed + ## with an exponent rather than an SI prefix, regardless of whether + ## `siPrefix` is true. + ## + ## If `unit` is not nil, the provided unit will be appended to the string + ## (with a space as required by the SI standard). This behaviour is slightly + ## different to appending the unit to the result as the location of the space + ## is altered depending on whether there is an exponent. + ## + ## .. code-block:: nim + ## + ## formatEng(4100, siPrefix=true, unit="V") == "4.1 kV" + ## formatEng(4.1, siPrefix=true, unit="V") == "4.1 V" + ## formatEng(4.1, siPrefix=true) == "4.1" # Note lack of space + ## formatEng(4100, siPrefix=true) == "4.1 k" + ## formatEng(4.1, siPrefix=true, unit="") == "4.1 " # Space with unit="" + ## formatEng(4100, siPrefix=true, unit="") == "4.1 k" + ## formatEng(4100) == "4.1e3" + ## formatEng(4100, unit="V") == "4.1e3 V" + ## formatEng(4100, unit="") == "4.1e3 " # Space with unit="" + ## + ## `decimalSep` is used as the decimal separator + var + absolute: BiggestFloat + significand: BiggestFloat + fexponent: BiggestFloat + exponent: int + splitResult: seq[string] + suffix: string = "" + proc getPrefix(exp: int): char = + ## Get the SI prefix for a given exponent + ## + ## Assumes exponent is a multiple of 3; returns ' ' if no prefix found + const siPrefixes = ['a','f','p','n','u','m',' ','k','M','G','T','P','E'] + var index: int = (exp div 3) + 6 + result = ' ' + if index in low(siPrefixes)..high(siPrefixes): + result = siPrefixes[index] + + # Most of the work is done with the sign ignored, so get the absolute value + absolute = abs(f) + significand = f + + if absolute == 0.0: + # Simple case: just format it and force the exponent to 0 + exponent = 0 + result = significand.formatBiggestFloat(ffDecimal, precision, decimalSep='.') + else: + # Find the best exponent that's a multiple of 3 + fexponent = round(floor(log10(absolute))) + fexponent = 3.0 * round(floor(fexponent / 3.0)) + # Adjust the significand for the new exponent + significand /= pow(10.0, fexponent) + + # Round the significand and check whether it has affected + # the exponent + significand = round(significand, precision) + absolute = abs(significand) + if absolute >= 1000.0: + significand *= 0.001 + fexponent += 3 + # Components of the result: + result = significand.formatBiggestFloat(ffDecimal, precision, decimalSep='.') + exponent = fexponent.int() + + splitResult = result.split('.') + result = splitResult[0] + # result should have at most one decimal character + if splitResult.len() > 1: + # If trim is set, we get rid of trailing zeros. Don't use trimZeros here as + # we can be a bit more efficient through knowledge that there will never be + # an exponent in this part. + if trim: + while splitResult[1].endsWith("0"): + # Trim last character + splitResult[1].setLen(splitResult[1].len-1) + if splitResult[1].len() > 0: + result &= decimalSep & splitResult[1] + else: + result &= decimalSep & splitResult[1] + + # Combine the results accordingly + if siPrefix and exponent != 0: + var p = getPrefix(exponent) + if p != ' ': + suffix = " " & p + exponent = 0 # Exponent replaced by SI prefix + if suffix == "" and unit != nil: + suffix = " " + if unit != nil: + suffix &= unit + if exponent != 0: + result &= "e" & $exponent + result &= suffix + proc findNormalized(x: string, inArray: openArray[string]): int = var i = 0 while i < high(inArray): @@ -1864,4 +2000,33 @@ bar doAssert s.split(' ', maxsplit=4) == @["", "this", "", "", "is an example "] doAssert s.split(" ", maxsplit=4) == @["", "this", "", "", "is an example "] + block: # formatEng tests + doAssert formatEng(0, 2, trim=false) == "0.00" + doAssert formatEng(0, 2) == "0" + doAssert formatEng(53, 2, trim=false) == "53.00" + doAssert formatEng(0.053, 2, trim=false) == "53.00e-3" + doAssert formatEng(0.053, 4, trim=false) == "53.0000e-3" + doAssert formatEng(0.053, 4, trim=true) == "53e-3" + doAssert formatEng(0.053, 0) == "53e-3" + doAssert formatEng(52731234) == "52.731234e6" + doAssert formatEng(-52731234) == "-52.731234e6" + doAssert formatEng(52731234, 1) == "52.7e6" + doAssert formatEng(-52731234, 1) == "-52.7e6" + doAssert formatEng(52731234, 1, decimalSep=',') == "52,7e6" + doAssert formatEng(-52731234, 1, decimalSep=',') == "-52,7e6" + + doAssert formatEng(4100, siPrefix=true, unit="V") == "4.1 kV" + doAssert formatEng(4.1, siPrefix=true, unit="V") == "4.1 V" + doAssert formatEng(4.1, siPrefix=true) == "4.1" # Note lack of space + doAssert formatEng(4100, siPrefix=true) == "4.1 k" + doAssert formatEng(4.1, siPrefix=true, unit="") == "4.1 " # Includes space + doAssert formatEng(4100, siPrefix=true, unit="") == "4.1 k" + doAssert formatEng(4100) == "4.1e3" + doAssert formatEng(4100, unit="V") == "4.1e3 V" + doAssert formatEng(4100, unit="") == "4.1e3 " # Space with unit="" + # Don't use SI prefix as number is too big + doAssert formatEng(3.1e22, siPrefix=true, unit="a") == "31e21 a" + # Don't use SI prefix as number is too small + doAssert formatEng(3.1e-25, siPrefix=true, unit="A") == "310e-27 A" + #echo("strutils tests passed") diff --git a/web/news.txt b/web/news.txt index 2ede07151..12f08e5eb 100644 --- a/web/news.txt +++ b/web/news.txt @@ -70,6 +70,8 @@ Library Additions into an integer part and a floating part (in the range -1<x<1). - Added ``trimZeros`` to ```strutils.nim`` to trim trailing zeros in a floating point number. +- Added ``formatEng`` to ``strutils.nim`` to format numbers using engineering + notation. Compiler Additions |