Standard library · Basics

fmt

Turning numbers and booleans into text, aligning text, and building a string from a template.

import fmt

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Functions

When you want tidy, readable output, the fmt package is what you reach for. With it you turn numbers into text, line text up in fixed-width columns, and build sentences from a template.

The templates are simple: every {} in the template is filled with the next element of the vector of values. Since the values are strings, convert numbers first with a function such as Int.

Functions

`Int`

func Int(i: i64): str

Turns a whole number into text, with a minus sign where one is needed.

fmt-Int.salam

import fmt

func main:
    println "[" + fmt.Int(-42) + "]"
    println "[" + fmt.Uint(42 as u64) + "]"
    println "[" + fmt.Float(3.25) + "]"
    println "[" + fmt.FloatPrec(3.14159, 2) + "]"
    println "[" + fmt.Bool(true) + "]"
    println "[" + fmt.Hex(255 as u64) + "]"
end

Output[-42] [42] [3.25] [3.14] [true] [ff]

`Float`

func Float(f: f64): str

Turns a decimal number into text and leaves off the useless trailing digits.

The example for this item is shown with the ones above: fmt-Int.salam

`Bool`

func Bool(b: bool): str

Turns a boolean into "true" or "false".

The example for this item is shown with the ones above: fmt-Int.salam

`PadLeft`

func PadLeft(s: str, width: int): str

If the text is shorter than width, adds spaces on its left until it reaches that width. The width counts characters, so it behaves correctly outside ASCII too. In a column of numbers this is what lines them up on the right.

fmt-PadLeft.salam

import fmt

func main:
    println "[" + fmt.PadLeft("42", 6) + "]"
    println "[" + fmt.PadRight("42", 6) + "]"
    println "[" + fmt.Center("42", 6) + "]"
    println "[" + fmt.PadLeft("salam", 10) + "]"
end

Output[ 42] [42 ] [ 42 ] [ salam]

`PadRight`

func PadRight(s: str, width: int): str

Like PadLeft, but puts the spaces on the right of the text.

The example for this item is shown with the ones above: fmt-PadLeft.salam

`Center`

func Center(s: str, width: int): str

Places the text in the middle of the given width. When the padding does not divide evenly, the extra space goes on the right.

The example for this item is shown with the ones above: fmt-PadLeft.salam

`Sprintf`

func Sprintf(tmpl: str, args: Vector<str>): str

Takes the template and fills each {} in turn from the args vector. If the values run out the remaining holes are left empty, and extra values are ignored.

fmt-Sprintf.salam

import fmt

func main:
    mut values := Vector {} as Vector<str>
    defer values.free()
    values.push("Sara")
    values.push(fmt.Int(19))
    println fmt.Sprintf("{} scored {}.", values)
end

OutputSara scored 19.

`Fprintf`

func Fprintf(f: File*, tmpl: str, args: Vector<str>): int

Like Sprintf, but writes the result straight into an open file and returns the number of bytes written.

fmt-Fprintf.salam

import fmt
import io
import os

func main:
    mut values := Vector {} as Vector<str>
    defer values.free()
    values.push("25")
    f := os.Open("temperature.txt", "wb")
    fmt.Fprintf(f, "today it is {} degrees\n", values)
    io.Close(f)
    print io.ReadFile("temperature.txt")
end

Outputtoday it is 25 degrees

`FloatPrec`

func FloatPrec(f: f64, prec: int): str

Turns a decimal number into text with the number of decimal places you ask for, rounding it.

The example for this item is shown with the ones above: fmt-Int.salam

`Uint`

func Uint(u: u64): str

Turns an unsigned 64-bit number into text, for numbers too large to fit in an i64.

The example for this item is shown with the ones above: fmt-Int.salam

`Hex`

func Hex(u: u64): str

Writes the number in base sixteen in lower case, with no 0x prefix.

The example for this item is shown with the ones above: fmt-Int.salam