Format a text in GO better than fmt

Format a text in GO better then fmt

Looking at the article title, we should clarify what means better and what is text formatting. Lets start from the last one from these these theses. Text formatting is an important part of programming, prepared text is using in a various tasks:

• description/result of some operations;
• detailed log;
• as a query for data selection in other systems;
• and in many others fields. Better means that sf (wissance.StringFormatter) has features that fmt has't (see chapter 1 to see our text formatting approach).

1. What can do sf aka wissance.stringFormatter

In our earlier article we were writing about sf convinience (convenience is a thing that is subjective to humans; here, I mean convenience based on my own background). But briefly it is more covnenient to format text like:

userNews = stringFormatter.Format("Hi \"{0}\", see latest news: {1}", "john doe", "1. You won 1M$ in a lottery, please give us your VISA/MS card data to receive money.")

then like:

userNews = fmt.Sprintf("Hi \"%s\", see latest news: %s", "john doe", "1. You won 1M$ in a lottery, please give us your VISA/MS card data to receive money.")

Until version 1.2.0 sf was unable to make more precise argument formatting (i.e., use different number notation: bin, hex), starting with 1.2.0 we could do almost all that fmt supports:

1. Bin number formatting:
   • {0:B}, 15 outputs -> 1111
   • {0:B8}, 15 outputs -> 00001111
2. Hex number formatting
   • {0:X}, 250 outputs -> fa
   • {0:X4}, 250 outputs -> 00fa
3. Oct number formatting
   • {0:o}, 11 outputs -> 14
4. Float point number formatting
   • {0:E2}, 191.0478 outputs -> 1.91e+02
   • {0:F}, 10.4567890 outputs -> 10.456789
   • {0:F4}, 10.4567890 outputs -> 10.4568
   • {0:F8}, 10.4567890 outputs -> 10.45678900
5. Percentage output
   • {0:P100}, 12 outputs -> 12%

sf has 2 string format methods - Format and FormatComplex. Latter also allows passing argument formatting, like for Format method.

Let's consider a minimal example:

1. We should build text using the following format "Today tempearture is {temp}, humidity is {hum} where {temp} and {hum} should be replaced with an actual sensor values.
2. We would like to specify {temp} and {hum} output, i.e., {temp} should have 4 digits after the dot, and {hum} must be outputted in percents. After analyzing these requirements, we modified our template as follows: "Today tempearture is {temp:F4}, humidity is {hum:P100}".
3. Passing 12.3456 and 60 like this:

   sf.FormatComplex("Today tempearture is {temp:F4}, humidity is {hum:P100}", map[string]any {"temp":12.3456, "hum":60})

More examples could be found in a FormatComplex unit test, see in repo and below:

func TestFormatComplexWithArgFormatting(t *testing.T) {
    for name, test := range map[string]struct {
        template string
        args     map[string]any
        expected string
    }{
        "numeric_test_1": {
            template: "This is the text with an only number formatting: scientific - {mass} / {mass : e2}",
            args:     map[string]any{"mass": 191.0784},
            expected: "This is the text with an only number formatting: scientific - 191.0784 / 1.91e+02",
        },
        "numeric_test_2": {
            template: "This is the text with an only number formatting: binary - {bin:B} / {bin : B8}, hexadecimal - {hex:X} / {hex : X4}",
            args:     map[string]any{"bin": 15, "hex": 250},
            expected: "This is the text with an only number formatting: binary - 1111 / 00001111, hexadecimal - fa / 00fa",
        },
        "numeric_test_3": {
            template: "This is the text with an only number formatting: decimal - {float:F} / {float : F4} / {float:F8}",
            args:     map[string]any{"float": 10.5467890},
            expected: "This is the text with an only number formatting: decimal - 10.546789 / 10.5468 / 10.54678900",
        },
    } {
        t.Run(name, func(t *testing.T) {
            assert.Equal(t, test.expected, stringFormatter.FormatComplex(test.template, test.args))
        })
    }
}

It is clear that we've got convenient (for people with C#, Python background) library for text formatting. But we have another advantage - performance, sf makes formatting **FASTER than fmt**.

2. Perforamnce Benefits

There is one more important thing that could distinguish a sf library: it has performance advances, both in formatting cases with argument format specifications and without them. But FormatComplex is twice faster than fmt, see picture below with the results:

3. Conclusion

Today we could say that there is one more text formatting utility/lib that has all fmt features, and this library processes text faster, which in some cases could be important. Please give us a star on GitHub and subscribe.