README
¶
encode/format
Subset port of d3-format + a strftime-style mini-mapping for time formats. Pure stdlib; no external date library.
Supported number specifiers
| Spec | Input | Output | Notes |
|---|---|---|---|
f |
1234.5 | 1234.500000 |
Default 6-decimal fixed point. |
.2f |
1234.5 | 1234.50 |
Fixed-point with 2 decimals. |
,.2f |
1234.5 | 1,234.50 |
Thousands separator + 2 decimals. |
% |
0.123 | 12.3% |
Default 1-decimal percent. |
.0% |
0.123 | 12% |
Zero-decimal percent. |
,d |
1234567 | 1,234,567 |
Integer with thousands. |
d |
3.6 | 4 |
Integer (round-to-nearest). |
.3e |
1234.5 | 1.235e+03 |
Scientific with 3 decimals. |
.0s |
1234 | 1k |
SI prefix (no decimals). |
.2s |
1234 | 1.23k |
SI prefix with 2 decimals. |
| (empty) | 3.14159 | 3.14159 |
Default %g rendering. |
Supported time directives
Time specs are detected by the presence of any %X directive other
than a bare % or the number-percent N%.
| Directive | Maps to Go layout | Renders |
|---|---|---|
%Y |
2006 |
4-digit year |
%m |
01 |
2-digit month |
%d |
02 |
2-digit day |
%H |
15 |
2-digit hour (24h) |
%M |
04 |
2-digit minute |
%S |
05 |
2-digit second |
%L |
000 |
3-digit millisecond |
%j |
002 |
3-digit day-of-year |
%% |
% |
literal % |
Examples
Parse(",.2f").Apply(1234.5) → "1,234.50"
Parse(".0%").Apply(0.123) → "12%"
Parse("%Y-%m-%d").Apply(t) → "2026-05-19"
Parse("%H:%M").Apply(t) → "14:30"
Error handling
A malformed spec returns PRISM_SPEC_011 with the spec string + parse
reason in the error context. Empty spec → no-op (default %g).
Out of scope
The full d3-format grammar (fill, align, sign, symbol, width, type 'b', type 'r', etc.) is not ported. Add a specifier branch + test when a real fixture needs it. The 90% subset above covers every test gate in P06.
Documentation
¶
Overview ¶
Package format implements a small subset of the d3-format mini-DSL plus a strftime-style mini-mapping for time formats. Pure stdlib. See README.md for the supported specifier set.
Number specifier grammar (subset):
[,]?[.<int>]?[Nf|N%|%|d|Ne|Ns]
, thousands separator
.N precision (digits after decimal, or significant figures for s)
f fixed-point ("1234.50")
% percent (multiply by 100, append "%")
d integer
e scientific ("1.234e+03")
s SI prefix ("1k", "1.2M")
Time specifier grammar (subset of strftime):
%Y 4-digit year %m 2-digit month %d 2-digit day-of-month %H 2-digit hour (24h) %M 2-digit minute %S 2-digit second %L 3-digit millisecond %j 3-digit day-of-year
The discriminator between number/time format is the presence of a `%X` directive that is not a bare "%" or "N%" — i.e. anything containing `%Y`, `%m`, etc. is a time format.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type NumberSpec ¶
type NumberSpec struct {
Thousands bool
Precision int // -1 = unset
HasPrec bool // distinguishes ".0f" from "f"
Type byte // 'f' | '%' | 'd' | 'e' | 's'
}
NumberSpec captures the parsed number format.
type Spec ¶
type Spec struct {
Raw string
Number *NumberSpec
Time *TimeSpec
}
Spec is a parsed format specifier. Either Number or Time is set, never both.
Source Files