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Re-apply patch from ff8924ce16 to dev manual

This commit is contained in:
Aleksey Tsalolikhin
2020-08-06 15:28:44 -07:00
committed by William Langford
parent d57d9737d7
commit 9600a5c781

View File

@@ -304,11 +304,37 @@ sections:
program can be a useful way of formatting JSON output from,
say, `curl`.
An important point about the identity filter is that it
guarantees to preserve the literal decimal representation
of values. This is particularly important when dealing with numbers
which can't be losslessly converted to an IEEE754 double precision
representation.
jq doesn't truncate the literal numbers to double unless there
is a need to make arithmetic operations with the number.
Comparisions are carried out over the untruncated big decimal
representation of the number.
jq will also try to maintain the original decimal precision of the provided
number literal. See below for examples.
examples:
- program: '.'
input: '"Hello, world!"'
output: ['"Hello, world!"']
- program: '. | tojson'
input: '12345678909876543212345'
output: ['"12345678909876543212345"']
- program: 'map([., . == 1]) | tojson'
input: '[1, 1.000, 1.0, 100e-2]'
output: ['"[[1,true],[1.000,true],[1.0,true],[1.00,true]]"']
- program: '. as $big | [$big, $big + 1] | map(. > 10000000000000000000000000000000)'
input: '10000000000000000000000000000001'
output: ['[true, false]']
- title: "Object Identifier-Index: `.foo`, `.foo.bar`"
body: |
@@ -524,6 +550,16 @@ sections:
expression that takes an input, ignores it, and returns 42
instead.
Numbers in jq are internally represented by their IEEE754 double
precision approximation. Any arithmetic operation with numbers,
whether they are literals or results of previous filters, will
produce a double precision floating point result.
However, when parsing a literal jq will store the original literal
string. If no mutation is applied to this value then it will make
to the output in its original form, even if conversion to double
would result in a loss.
entries:
- title: "Array construction: `[]`"
body: |
@@ -655,6 +691,18 @@ sections:
try to add a string to an object you'll get an error message and
no result.
Please note that all numbers are converted to IEEE754 double precision
floating point representation. Arithmetic and logical operators are working
with these converted doubles. Results of all such operations are also limited
to the double precision.
The only exception to this behaviour of number is a snapshot of original number
literal. When a number which originally was provided as a literal is never
mutated until the end of the program then it is printed to the output in its
original literal form. This also includes cases when the original literal
would be truncated when converted to the IEEE754 double precision floating point
number.
entries:
- title: "Addition: `+`"
body: |