fmt

The fmt package formats strings with % specifiers, like printf in C. Pass the values as a list.

println fmt::sprintf("Hello, %s!", ["World"])            # Hello, World!
println fmt::sprintf("%d + %d = %d", [1, 2, 3])          # 1 + 2 = 3
println fmt::sprintf("Pi: %.4f", [3.14159265])           # Pi: 3.1416
println fmt::sprintf("|%-10s|%10s|", ["left", "right"])  # |left      |     right|
println fmt::sprintf("%08d", [42])                       # 00000042
println fmt::sprintf("0x%x 0%o %b", [255, 255, 255])     # 0xff 0377 11111111

fmt::printlnf("User: %s, score: %d", ["Alice", 99])      # User: Alice, score: 99

printf prints without a trailing newline and printlnf with one.

Specifiers

Specifier	Formats
%s	A string, or any value converted to a string
%d, %i	An integer
%f	A float, with 6 decimal places unless a precision is given
%e	A float in scientific notation, with 6 decimal places unless a precision is given
%x, %X	Hexadecimal, lower or upper case
%o	Octal
%b	Binary
%c	The character for a code point
%%	A literal %

Between the % and the letter you can add:

Flag	Meaning	Example
A number	Minimum width, right-aligned	%10s
-	Left-align within the width	%-10s
0	Pad numbers with zeros	%08d
+	Always show the sign	%+d
.N	Decimal places for %f and %e, or maximum length for %s	%.2f, %.3s

println fmt::sprintf("%e", [12345.678])   # 1.234568e+04
println fmt::sprintf("%.2e", [0.00012])   # 1.20e-04

For most formatting, string interpolation and .to_string(format) are simpler. For templates with named placeholders, see template.

Functions

fmt::sprintf

fmt::sprintf(format_str, args = [])

Formats a string using printf-style format specifiers.

Parameter	Type	Default	Description
format_str	string		Format string with % specifiers.
args	list	[]	List of values to format.

Returns string — The formatted string.

import fmt
println fmt::sprintf("Hello, %s! You are %d years old.", ["Alice", 30])
println fmt::sprintf("Pi is approximately %.4f", [3.14159265])
println fmt::sprintf("Hex: %x  Oct: %o  Bin: %b", [255, 255, 255])
println fmt::sprintf("%-10s|%10s", ["left", "right"])

fmt::printf

fmt::printf(format_str, args = [])

Formats and prints to stdout (no newline).

Parameter	Type	Default	Description
format_str	string		Format string.
args	list	[]	Arguments list.

fmt::printlnf

fmt::printlnf(format_str, args = [])

Formats and prints to stdout with a newline.

Parameter	Type	Default	Description
format_str	string		Format string.
args	list	[]	Arguments list.