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Amend fmt documentation

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Feoramund
2024-05-09 18:40:30 -04:00
parent 8c111f1baf
commit 11180e36ae
1 changed files with 18 additions and 15 deletions
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33
core/fmt/doc.odin
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@@ -1,5 +1,5 @@
/*
package fmt implemented formatted I/O with procedures similar to C's printf and Python's format.
package fmt implements formatted I/O with procedures similar to C's printf and Python's format.
The format 'verbs' are derived from C's but simpler.
Printing
@@ -33,6 +33,8 @@ Floating-point, complex numbers, and quaternions:
%E scientific notation, e.g. -1.23456E+78
%f decimal point but no exponent, e.g. 123.456
%F synonym for %f
%g synonym for %f with default maximum precision
%G synonym for %g
%h hexadecimal (lower-case) representation with 0h prefix (0h01234abcd)
%H hexadecimal (upper-case) representation with 0H prefix (0h01234ABCD)
%m number of bytes in the best unit of measurement, e.g. 123.45mib
@@ -61,9 +63,9 @@ For compound values, the elements are printed using these rules recursively; lai
bit sets {key0 = elem0, key1 = elem1, ...}
pointer to above: &{}, &[], &map[]
Width is specified by an optional decimal number immediately preceding the verb.
Width is specified by an optional decimal number immediately after the '%'.
If not present, the width is whatever is necessary to represent the value.
Precision is specified after the (optional) width followed by a period followed by a decimal number.
Precision is specified after the (optional) width by a period followed by a decimal number.
If no period is present, a default precision is used.
A period with no following number specifies a precision of 0.
@@ -75,7 +77,7 @@ Examples:
%8.f width 8, precision 0
Width and precision are measured in units of Unicode code points (runes).
n.b. C's printf uses units of bytes
n.b. C's printf uses units of bytes.
Other flags:
@@ -92,7 +94,7 @@ Other flags:
0 pad with leading zeros rather than spaces
Flags are ignored by verbs that don't expect them
Flags are ignored by verbs that don't expect them.
For each printf-like procedure, there is a print function that takes no
@@ -105,19 +107,20 @@ Explicit argument indices:
In printf-like procedures, the default behaviour is for each formatting verb to format successive
arguments passed in the call. However, the notation [n] immediately before the verb indicates that
the nth zero-index argument is to be formatted instead.
The same notation before an '*' for a width or precision selecting the argument index holding the value.
Python-like syntax with argument indices differs for the selecting the argument index: {N:v}
The same notation before an '*' for a width or precision specifier selects the argument index
holding the value.
Python-like syntax with argument indices differs for selecting the argument index: {n:v}
Examples:
fmt.printf("%[1]d %[0]d\n", 13, 37); // C-like syntax
fmt.printf("{1:d} {0:d}\n", 13, 37); // Python-like syntax
fmt.printfln("%[1]d %[0]d", 13, 37) // C-like syntax
fmt.printfln("{1:d} {0:d}", 13, 37) // Python-like syntax
prints "37 13", whilst:
fmt.printf("%[2]*.[1]*[0]f\n", 17.0, 2, 6); // C-like syntax
fmt.printf("%{0:[2]*.[1]*f}\n", 17.0, 2, 6); // Python-like syntax
equivalent to:
fmt.printf("%6.2f\n", 17.0, 2, 6); // C-like syntax
fmt.printf("{:6.2f}\n", 17.0, 2, 6); // Python-like syntax
prints "17.00"
fmt.printfln("%*[2].*[1][0]f", 17.0, 2, 6) // C-like syntax
fmt.printfln("{0:*[2].*[1]f}", 17.0, 2, 6) // Python-like syntax
is equivalent to:
fmt.printfln("%6.2f", 17.0) // C-like syntax
fmt.printfln("{:6.2f}", 17.0) // Python-like syntax
and prints "17.00".
Format errors: