freebsd-dev/gnu/usr.bin/awk/POSIX
1993-06-18 04:22:21 +00:00

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Right now, the numeric vs. string comparisons are screwed up in draft
11.2. What prompted me to check it out was the note in gnu.bug.utils
which observed that gawk was doing the comparison $1 == "000"
numerically. I think that we can agree that intuitively, this should
be done as a string comparison. Version 2.13.2 of gawk follows the
current POSIX draft. Following is how I (now) think this
stuff should be done.
1. A numeric literal or the result of a numeric operation has the NUMERIC
attribute.
2. A string literal or the result of a string operation has the STRING
attribute.
3. Fields, getline input, FILENAME, ARGV elements, ENVIRON elements and the
elements of an array created by split() that are numeric strings
have the STRNUM attribute. Otherwise, they have the STRING attribute.
Uninitialized variables also have the STRNUM attribute.
4. Attributes propagate across assignments, but are not changed by
any use. (Although a use may cause the entity to acquire an additional
value such that it has both a numeric and string value -- this leaves the
attribute unchanged.)
When two operands are compared, either string comparison or numeric comparison
may be used, depending on the attributes of the operands, according to the
following (symmetric) matrix:
+----------------------------------------------
| STRING NUMERIC STRNUM
--------+----------------------------------------------
|
STRING | string string string
|
NUMERIC | string numeric numeric
|
STRNUM | string numeric numeric
--------+----------------------------------------------
So, the following program should print all OKs.
echo '0e2 0a 0 0b
0e2 0a 0 0b' |
$AWK '
NR == 1 {
num = 0
str = "0e2"
print ++test ": " ( (str == "0e2") ? "OK" : "OOPS" )
print ++test ": " ( ("0e2" != 0) ? "OK" : "OOPS" )
print ++test ": " ( ("0" != $2) ? "OK" : "OOPS" )
print ++test ": " ( ("0e2" == $1) ? "OK" : "OOPS" )
print ++test ": " ( (0 == "0") ? "OK" : "OOPS" )
print ++test ": " ( (0 == num) ? "OK" : "OOPS" )
print ++test ": " ( (0 != $2) ? "OK" : "OOPS" )
print ++test ": " ( (0 == $1) ? "OK" : "OOPS" )
print ++test ": " ( ($1 != "0") ? "OK" : "OOPS" )
print ++test ": " ( ($1 == num) ? "OK" : "OOPS" )
print ++test ": " ( ($2 != 0) ? "OK" : "OOPS" )
print ++test ": " ( ($2 != $1) ? "OK" : "OOPS" )
print ++test ": " ( ($3 == 0) ? "OK" : "OOPS" )
print ++test ": " ( ($3 == $1) ? "OK" : "OOPS" )
print ++test ": " ( ($2 != $4) ? "OK" : "OOPS" ) # 15
}
{
a = "+2"
b = 2
if (NR % 2)
c = a + b
print ++test ": " ( (a != b) ? "OK" : "OOPS" ) # 16 and 22
d = "2a"
b = 2
if (NR % 2)
c = d + b
print ++test ": " ( (d != b) ? "OK" : "OOPS" )
print ++test ": " ( (d + 0 == b) ? "OK" : "OOPS" )
e = "2"
print ++test ": " ( (e == b "") ? "OK" : "OOPS" )
a = "2.13"
print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" )
a = "2.130000"
print ++test ": " ( (a != 2.13) ? "OK" : "OOPS" )
if (NR == 2) {
CONVFMT = "%.6f"
print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" )
}
}'