fmt

The fmt package provides sprintf-style string formatting with % format specifiers, along with printf and printlnf convenience functions.

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Format Specifiers

Specifier	Description
%s	String
%d, %i	Signed decimal integer
%f	Floating-point (default 6 decimal places)
%e	Scientific notation
%x	Lowercase hexadecimal integer
%X	Uppercase hexadecimal integer
%o	Octal integer
%b	Binary integer
%c	Character from codepoint
%%	Literal %

Flags and Width

Flags appear between % and the specifier:

Flag	Description
N	Minimum field width (e.g. %10s right-aligns in 10 chars)
-	Left-align within the field width
0	Zero-pad numbers to the field width
+	Always show sign for numeric values
.N	Precision: decimal places for %f/%e, max chars for %s

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Package Functions

sprintf(format_str, args?)

Formats a string using % specifiers.

Parameters

Type	Name	Description	Default
string	format_str	Format string with % specifiers	—
list	args	Values to substitute, in order	[]

Returns

Type	Description
string	Formatted string

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printf(format_str, args?)

Formats and prints to stdout without a trailing newline.

Parameters Same as sprintf.

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printlnf(format_str, args?)

Formats and prints to stdout with a trailing newline.

Parameters Same as sprintf.

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Examples

import "fmt"

# Basic substitution
println fmt::sprintf("Hello, %s!", ["World"])          # Hello, World!

# Integers and floats
println fmt::sprintf("%d + %d = %d", [1, 2, 3])        # 1 + 2 = 3
println fmt::sprintf("Pi: %.4f", [3.14159265])          # Pi: 3.1416

# Width and alignment
println fmt::sprintf("|%-10s|%10s|", ["left", "right"]) # |left      |     right|
println fmt::sprintf("%08d", [42])                      # 00000042

# Number bases
println fmt::sprintf("0x%x  0%o  %b", [255, 255, 255]) # 0xff  0377  11111111

# Scientific notation
println fmt::sprintf("%.2e", [123456.789])              # 1.23e+05

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