PowerShell, formatting values in another culture

Question

Is there an easy way in PowerShell to format numbers and the like in another locale? I'm currently writing a few functions to ease SVG generation for me and SVG uses . as a decimal separator, while PowerShell honors my locale settings (de-DE) when converting floating-point numbers to strings.

Is there an easy way to set another locale for a function or so without sticking

.ToString((New-Object Globalization.CultureInfo ""))

after every double variable?

Note: This is about the locale used for formatting, not the format string.

(Side question: Should I use the invariant culture in that case or rather en-US?)

ETA: Well, what I'm trying here is something like the following:

function New-SvgWave([int]$HalfWaves, [double]$Amplitude, [switch]$Upwards) {
    "<path d='M0,0q0.5,{0} 1,0{1}v1q-0.5,{2} -1,0{3}z'/>" -f (
        $(if ($Upwards) {-$Amplitude} else {$Amplitude}),
        ("t1,0" * ($HalfWaves - 1)),
        $(if ($Upwards -xor ($HalfWaves % 2 -eq 0)) {-$Amplitude} else {$Amplitude}),
        ("t-1,0" * ($HalfWaves - 1))
    )
}

Just a little automation for stuff I tend to write all the time and the double values need to use the decimal point instead of a comma (which they use in my locale).

ETA2: Interesting trivia to add:

PS Home:> $d=1.23
PS Home:> $d
1,23
PS Home:> "$d"
1.23

By putting the variable into a string the set locale doesn't seem to apply, somehow.

Answer 1

If you already have the culture loaded in your environment,

    #>Get-Culture
    LCID             Name             DisplayName                                                                                                                                             
----             ----             -----------                                                                                                                                             
1031             de-DE            German (Germany)                                                                                                                                        

#>Get-UICulture

LCID             Name             DisplayName                                                                                                                                             
----             ----             -----------                                                                                                                                             
1033             en-US            English (United States) 

it is possible to resolve this problem:

PS Home:> $d=1.23
PS Home:> $d
1,23

like this:

$d.ToString([cultureinfo]::CurrentUICulture)
1.23

Of course you need to keep in mind that if other users run the script with a different locale setting, the results may not turn out as originally intended.

Nevertheless, this solution could come in useful. Have fun!

Answer 2

While Keith Hill's helpful answer shows you how to change a script's current culture on demand (more modern alternative as of PSv3+ and .NET framework v4.6+:
[cultureinfo]::CurrentCulture = [cultureinfo]::InvariantCulture), there is no need to change the culture, because - as you've discovered in your second update to the question - PowerShell's string interpolation (as opposed to using the -f operator) always uses the invariant rather than the current culture:

In other words:

If you replace 'val: {0}' -f 1.2 with "val: $(1.2)", the literal 1.2 is not formatted according to the rules of the current culture.
You can verify in the console by running (on a single line; PSv3+, .NET framework v4.6+):

 PS> [cultureinfo]::currentculture = 'de-DE'; 'val: {0}' -f 1.2; "val: $(1.2)"
 val: 1,2 # -f operator: GERMAN culture applies, where ',' is the decimal mark
 val: 1.2 # string interpolation: INVARIANT culture applies, where '.' is the decimal mark.

---

Background:

Surprisingly, PowerShell always applies the invariant rather than the current culture in the following string-related contexts, if the type at hand supports culture-specific conversion to and from strings:

As explained in this in-depth answer, PowerShell explicitly requests culture-invariant processing - by passing the [cultureinfo]::InvariantCulture instance - in the following scenarios:

• When string-interpolating: if the object's type implements the IFormattable interface; otherwise, PowerShell calls .psobject.ToString() on the object.

• When casting:

  • to a string, including when binding to a [string]-typed parameter: if the source type implements the [IFormattable] interface; otherwise, PowerShell calls .psobject.ToString().
  • from a string: if the target type's static .Parse() method has an overload with an [IFormatProvider]-typed parameter (which is an interface implemented by [cultureinfo]).

• When string-comparing (-eq, -lt, -gt) , using the String.Compare() overload that accepts a CultureInfo parameter.

• Others?

As for what the invariant culture is / is for:

The invariant culture is culture-insensitive; it is associated with the English language but not with any country/region.
[...]
Unlike culture-sensitive data, which is subject to change by user customization or by updates to the .NET Framework or the operating system, invariant culture data is stable over time and across installed cultures and cannot be customized by users. This makes the invariant culture particularly useful for operations that require culture-independent results, such as formatting and parsing operations that persist formatted data, or sorting and ordering operations that require that data be displayed in a fixed order regardless of culture.

Presumably, it is the stability across cultures that motivated PowerShell's designers to consistently use the invariant culture when implicitly converting to and from strings.

For instance, if you hard-code a date string such as '7/21/2017' into a script and later try to convert it to date with a [date] cast, PowerShell's culture-invariant behavior ensures that the script doesn't break even when run while a culture other than US-English is in effect - fortunately, the invariant culture also recognizes ISO 8601-format date and time strings;
e.g., [datetime] '2017-07-21' works too.

On the flip side, if you do want to convert to and from current-culture-appropriate strings, you must do so explicitly.

To summarize:

• Converting to strings:

  • Embedding instances of data types with culture-sensitive-by-default string representations inside "..." yields a culture-invariant representation ([double] or [datetime] are examples of such types).
  • To get a current-culture representation, call .ToString() explicitly or use -f, the formatting operator (possibly inside "..." via an enclosing $(...)).

• Converting from strings:

  • A direct cast ([<type>] ...) only ever recognizes culture-invariant string representations.

  • To convert from a current-culture-appropriate string representation (or a specific culture's representation), use the target type's static ::Parse() method explicitly (optionally with an explicit [cultureinfo] instance to represent a specific culture).

---

Culture-INVARIANT examples:

• string interpolation and casts:

  • "$(1/10)" and [string] 1/10

    • both yield string literal 0.1, with decimal mark ., irrespective of the current culture.

  • Similarly, casts from strings are culture-invariant; e.g., [double] '1.2'

    • . is always recognized as the decimal mark, irrespective of the current culture.
    • Another way of putting it: [double] 1.2 is not translated to the culture-sensitive-by-default method overload [double]::Parse('1.2'), but to the culture-invariant [double]::Parse('1.2', [cultureinfo]::InvariantCulture)

• string comparison (assume that [cultureinfo]::CurrentCulture='tr-TR' is in effect - Turkish, where i is NOT a lowercase representation of I)

  • [string]::Equals('i', 'I', 'CurrentCultureIgnoreCase')
    • $false with the Turkish culture in effect.
    • 'i'.ToUpper() shows that in the Turkish culture the uppercase is İ, not I.
  • 'i' -eq 'I'
    • is still $true, because the invariant culture is applied.
    • implicitly the same as: [string]::Equals('i', 'I', 'InvariantCultureIgnoreCase')

---

Culture-SENSITIVE examples:

The current culture IS respected in the following cases:

• With -f, the string-formatting operator (as noted above):

  • [cultureinfo]::currentculture = 'de-DE'; '{0}' -f 1.2 yields 1,2
  • Pitfall: Due to operator precedence, any expression as the RHS of -f must be enclosed in (...) in order to be recognized as such:
    • E.g., '{0}' -f 1/10 is evaluated as if ('{0}' -f 1) / 10 had been specified;
      use '{0}' -f (1/10) instead.

• Default output to the console:

  • e.g., [cultureinfo]::CurrentCulture = 'de-DE'; 1.2 yields 1,2

  • The same applies to output from cmdlets; e.g.,
    [cultureinfo]::CurrentCulture = 'de-DE'; Get-Date '2017-01-01' yields
    Sonntag, 1. Januar 2017 00:00:00

  • Caveat: There appears to be a bug as of Windows PowerShell v5.1 / PowerShell Core v6.0.0-beta.5: in certain scenarios, literals passed to a script block as unconstrained parameters can result in culture-invariant default output - see this GitHub issue

• When writing to a file with Set-Content/Add-Content or Out-File / > / >>:

  • e.g., [cultureinfo]::CurrentCulture = 'de-DE'; 1.2 > tmp.txt; Get-Content tmp.txt yields 1,2

• When using the static ::Parse() / ::TryParse() methods on number types such as [double] while passing only the string to parse; e.g., with culture fr-FR in effect (where , is the decimal mark), [double]::Parse('1,2') returns double 1.2 (i.e., 1 + 2/10).

  • Caveat: As bviktor points out, thousands separators are recognized by default, but in a very loose fashion: effectively, the thousands separator can be placed anywhere inside the integer portion, irrespective of how many digits are in the resulting groups, and a leading 0 is also accepted; e.g., in the en-US culture (where , is the thousands separator), [double]::Parse('0,18') perhaps surprisingly succeeds and yields 18.
    • To suppress recognition of thousands separators, use something like [double]::Parse('0,18', 'Float'), via the NumberStyles parameter

• Unintentional culture-sensitivity that won't be corrected to preserve backward compatibility:

  • In parameter-binding type conversions for cmdlets (but not for functions) - see this GitHub issue.
  • In the -as operator - see this GitHub issue.
  • In [hashtable] key lookups - see this answer and this GitHub issue.

• Others?

Answer 3

This is a PowerShell function I use for testing script in other cultures. I believe it could be used for what you are after:

function Using-Culture ([System.Globalization.CultureInfo]$culture =(throw "USAGE: Using-Culture -Culture culture -Script {scriptblock}"),
                        [ScriptBlock]$script=(throw "USAGE: Using-Culture -Culture culture -Script {scriptblock}"))
{    
    $OldCulture = [System.Threading.Thread]::CurrentThread.CurrentCulture
    $OldUICulture = [System.Threading.Thread]::CurrentThread.CurrentUICulture
    try {
        [System.Threading.Thread]::CurrentThread.CurrentCulture = $culture
        [System.Threading.Thread]::CurrentThread.CurrentUICulture = $culture        
        Invoke-Command $script    
    }    
    finally {        
        [System.Threading.Thread]::CurrentThread.CurrentCulture = $OldCulture        
        [System.Threading.Thread]::CurrentThread.CurrentUICulture = $OldUICulture    
    }    
}

PS> $res = Using-Culture fr-FR { 1.1 }
PS> $res
1.1

Answer 4

I was thinking about how to make it easy and came up with accelerators:

Add-type -typedef @"
 using System;  

 public class InvFloat  
 {  
     double _f = 0;  
     private InvFloat (double f) {  
         _f = f;
     }  
     private InvFloat(string f) {  
         _f = Double.Parse(f, System.Globalization.CultureInfo.InvariantCulture);
     }  
     public static implicit operator InvFloat (double f) {  
         return new InvFloat(f);  
     }  
     public static implicit operator double(InvFloat f) {  
         return f._f;
     }  
     public static explicit operator InvFloat (string f) {  
         return new InvFloat (f);
     }  
     public override string ToString() { 
         return _f.ToString(System.Globalization.CultureInfo.InvariantCulture); 
     }
 }  
"@
$acce = [type]::gettype("System.Management.Automation.TypeAccelerators") 
$acce::Add('f', [InvFloat])
$y = 1.5.ToString()
$z = ([f]1.5).ToString()

I hope it will help.