| [3076] | 1 | March 2001:
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| 2 |
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| 3 | It looks like the revised 1003.2 standard will actually follow the
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| 4 | rules given below. Hallelujah!
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| 5 |
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| 6 | October 1998:
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| 7 |
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| 8 | The 1003.2 work has been at a stand-still for ages. Who knows if or
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| 9 | when a new revision will actually happen...
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| 10 |
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| 11 | August 1995:
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| 12 |
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| 13 | Although the published 1003.2 standard contained the incorrect
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| 14 | comparison rules of 11.2 draft as described below, no actual implementation
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| 15 | of awk (that I know of) actually used those rules.
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| 16 |
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| 17 | A revision of the 1003.2 standard is in progress, and in the May 1995
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| 18 | draft, the rules were fixed (based on my submissions for interpretation
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| 19 | requests) to match the description given below. Thus, the next version
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| 20 | of the standard will have a correct description of the comparison
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| 21 | rules.
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| 22 |
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| 23 | June 1992:
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| 24 |
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| 25 | Right now, the numeric vs. string comparisons are screwed up in draft
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| 26 | 11.2. What prompted me to check it out was the note in gnu.bug.utils
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| 27 | which observed that gawk was doing the comparison $1 == "000"
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| 28 | numerically. I think that we can agree that intuitively, this should
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| 29 | be done as a string comparison. Version 2.13.2 of gawk follows the
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| 30 | current POSIX draft. Following is how I (now) think this
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| 31 | stuff should be done.
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| 32 |
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| 33 | 1. A numeric literal or the result of a numeric operation has the NUMERIC
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| 34 | attribute.
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| 35 |
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| 36 | 2. A string literal or the result of a string operation has the STRING
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| 37 | attribute.
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| 38 |
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| 39 | 3. Fields, getline input, FILENAME, ARGV elements, ENVIRON elements and the
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| 40 | elements of an array created by split() that are numeric strings
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| 41 | have the STRNUM attribute. Otherwise, they have the STRING attribute.
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| 42 | Uninitialized variables also have the STRNUM attribute.
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| 43 |
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| 44 | 4. Attributes propagate across assignments, but are not changed by
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| 45 | any use. (Although a use may cause the entity to acquire an additional
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| 46 | value such that it has both a numeric and string value -- this leaves the
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| 47 | attribute unchanged.)
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| 48 |
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| 49 | When two operands are compared, either string comparison or numeric comparison
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| 50 | may be used, depending on the attributes of the operands, according to the
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| 51 | following (symmetric) matrix:
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| 52 |
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| 53 | +----------------------------------------------
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| 54 | | STRING NUMERIC STRNUM
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| 55 | --------+----------------------------------------------
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| 56 | |
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| 57 | STRING | string string string
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| 58 | |
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| 59 | NUMERIC | string numeric numeric
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| 60 | |
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| 61 | STRNUM | string numeric numeric
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| 62 | --------+----------------------------------------------
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| 63 |
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| 64 | So, the following program should print all OKs.
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| 65 |
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| 66 | echo '0e2 0a 0 0b
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| 67 | 0e2 0a 0 0b' |
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| 68 | $AWK '
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| 69 | NR == 1 {
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| 70 | num = 0
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| 71 | str = "0e2"
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| 72 |
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| 73 | print ++test ": " ( (str == "0e2") ? "OK" : "OOPS" )
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| 74 | print ++test ": " ( ("0e2" != 0) ? "OK" : "OOPS" )
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| 75 | print ++test ": " ( ("0" != $2) ? "OK" : "OOPS" )
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| 76 | print ++test ": " ( ("0e2" == $1) ? "OK" : "OOPS" )
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| 77 |
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| 78 | print ++test ": " ( (0 == "0") ? "OK" : "OOPS" )
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| 79 | print ++test ": " ( (0 == num) ? "OK" : "OOPS" )
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| 80 | print ++test ": " ( (0 != $2) ? "OK" : "OOPS" )
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| 81 | print ++test ": " ( (0 == $1) ? "OK" : "OOPS" )
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| 82 |
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| 83 | print ++test ": " ( ($1 != "0") ? "OK" : "OOPS" )
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| 84 | print ++test ": " ( ($1 == num) ? "OK" : "OOPS" )
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| 85 | print ++test ": " ( ($2 != 0) ? "OK" : "OOPS" )
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| 86 | print ++test ": " ( ($2 != $1) ? "OK" : "OOPS" )
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| 87 | print ++test ": " ( ($3 == 0) ? "OK" : "OOPS" )
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| 88 | print ++test ": " ( ($3 == $1) ? "OK" : "OOPS" )
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| 89 | print ++test ": " ( ($2 != $4) ? "OK" : "OOPS" ) # 15
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| 90 | }
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| 91 | {
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| 92 | a = "+2"
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| 93 | b = 2
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| 94 | if (NR % 2)
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| 95 | c = a + b
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| 96 | print ++test ": " ( (a != b) ? "OK" : "OOPS" ) # 16 and 22
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| 97 |
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| 98 | d = "2a"
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| 99 | b = 2
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| 100 | if (NR % 2)
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| 101 | c = d + b
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| 102 | print ++test ": " ( (d != b) ? "OK" : "OOPS" )
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| 103 |
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| 104 | print ++test ": " ( (d + 0 == b) ? "OK" : "OOPS" )
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| 105 |
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| 106 | e = "2"
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| 107 | print ++test ": " ( (e == b "") ? "OK" : "OOPS" )
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| 108 |
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| 109 | a = "2.13"
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| 110 | print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" )
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| 111 |
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| 112 | a = "2.130000"
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| 113 | print ++test ": " ( (a != 2.13) ? "OK" : "OOPS" )
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| 114 |
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| 115 | if (NR == 2) {
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| 116 | CONVFMT = "%.6f"
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| 117 | print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" )
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| 118 | }
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| 119 | }'
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