I didn't see anything in the gawk(1) manpage for doing this but it seems
like it should be possible.

ex. oz to lb using old-school units(1) command:
--
$ units -1 oz lb
* 0.0625

# this works:
$ echo "16 $(units -1 oz lb)" |awk '{print $1 " oz = " $1 * $3 " lb"}'
16 oz = 1 lb

# this does NOT work:
$ echo "16 $(units -1 oz lb)" |awk '{print $1 " oz = " $1 $2 $3 " lb"}'
16 oz = 16*0.0625 lb

--

Is there a way to tell (g)awk to interpret strings like "*", "/", "+",
"-", etc. as actual math operators or do I need to create a series of
tests of $2 in the above example?

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In article <tslgi7$3o0$1@nnrp.usenet.blueworldhosting.com>,
someone <someone@invalid.invalid> wrote:

ex. oz to lb using old-school units(1) command:

$ units -1 oz lb
* 0.0625

# this works:
$ echo "16 $(units -1 oz lb)" |awk '{print $1 " oz = " $1 * $3 " lb"}'
16 oz = 1 lb

# this does NOT work:
$ echo "16 $(units -1 oz lb)" |awk '{print $1 " oz = " $1 $2 $3 " lb"}'
16 oz = 16*0.0625 lb

Is there a way to tell (g)awk to interpret strings like "*", "/", "+",
"-", etc. as actual math operators

The short answer is "No". The slightly longer answer is "No, awk does not
have eval".

or do I need to create a series of
tests of $2 in the above example?

You could switch to Perl (which does have eval).

--
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In article <tsll3n$2drb$1@nnrp.usenet.blueworldhosting.com>,
someone <someone@invalid.invalid> wrote:

On 2/16/23 8:36 AM, Kenny McCormack wrote:

The short answer is "No". The slightly longer answer is "No, awk does not >> have eval".

Ah okay thanks; guess I wasn't missing something in the docs after all.

I don't really have practical reason for needing an eval() function, was
just something I came across while trying other things.

Yes, I get it. Although I've often wished AWK did have eval capability,
I've never really wanted it enough for it to be a deal-breaker. So, you
learn to live without it.

Incidentally, I was once told by an AWK developer that the hard part about implementing eval is if the thing you're eval'ing causes a new variable to spring into existence.

--
Trump - the President for the rest of us.

https://www.youtube.com/watch?v=JSkUJKgdcoE

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On 2/16/23 8:36 AM, Kenny McCormack wrote:

The short answer is "No". The slightly longer answer is "No, awk does not have eval".

Ah okay thanks; guess I wasn't missing something in the docs after all.

I don't really have practical reason for needing an eval() function, was
just something I came across while trying other things.

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On 2/16/2023 9:02 AM, someone wrote:

I didn't see anything in the gawk(1) manpage for doing this but it seems
like it should be possible.

It's not possible entirely within 1 call to awk but see https://stackoverflow.com/a/54161251/1745001 for a (slow) workaround.

Ed.

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On 2/16/23 12:16 PM, Ed Morton wrote:

On 2/16/2023 9:02 AM, someone wrote:

I didn't see anything in the gawk(1) manpage for doing this but it
seems like it should be possible.

It's not possible entirely within 1 call to awk but see https://stackoverflow.com/a/54161251/1745001 for a (slow) workaround.

    Ed.

Interesting -- I had been thinking about this earlier actually but I'm
not yet proficient enough to write functions like this. Bookmarked!

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although these strictly aren't "math operators", you can build an eval() function specifically for relational operators with a very short syntax :

function compare(__, _, ___) {
…. return +__==+___ \
….…. ? _ ~ "[^!]=" \
….…. : (_ ~ "[!=].|.>" || +__<+___)==(_<"=")
}


0x1.0FFFFp+22. <>. 11141110000000000e-10. . 1. 4456444. 1114111
0x1.0FFFFp+22. ==. 11141110000000000e-10. . 0. 4456444. 1114111
0x1.0FFFFp+22. !=. 11141110000000000e-10. . 1. 4456444. 1114111

0x1.0FFFFp+22. >. 11141110000000000e-10. . 1. 4456444. 1114111
0x1.0FFFFp+22. >=. 11141110000000000e-10. . 1. 4456444. 1114111
0x1.0FFFFp+22. <=. 11141110000000000e-10. . 0. 4456444. 1114111
0x1.0FFFFp+22. <. 11141110000000000e-10. . 0. 4456444. 1114111

0x1.0FFFFp+21. <>. 11141110000000000e-10. . 1. 2228222. 1114111
0x1.0FFFFp+21. ==. 11141110000000000e-10. . 0. 2228222. 1114111
0x1.0FFFFp+21. !=. 11141110000000000e-10. . 1. 2228222. 1114111

0x1.0FFFFp+21. >. 11141110000000000e-10. . 1. 2228222. 1114111
0x1.0FFFFp+21. >=. 11141110000000000e-10. . 1. 2228222. 1114111
0x1.0FFFFp+21. <=. 11141110000000000e-10. . 0. 2228222. 1114111
0x1.0FFFFp+21. <. 11141110000000000e-10. . 0. 2228222. 1114111

0x1.0FFFFp+20. <>. 11141110000000000e-10. . 0. 1114111. 1114111
0x1.0FFFFp+20. ==. 11141110000000000e-10. . 1. 1114111. 1114111
0x1.0FFFFp+20. !=. 11141110000000000e-10. . 0. 1114111. 1114111

0x1.0FFFFp+20. >. 11141110000000000e-10. . 0. 1114111. 1114111
0x1.0FFFFp+20. >=. 11141110000000000e-10. . 1. 1114111. 1114111
0x1.0FFFFp+20. <=. 11141110000000000e-10. . 1. 1114111. 1114111
0x1.0FFFFp+20. <. 11141110000000000e-10. . 0. 1114111. 1114111

0x1.0FFFFp+20. <>. 1114111000000000117E-12. 1. 1114111. 1114111.0000000002 0x1.0FFFFp+20. ==. 1114111000000000117E-12. 0. 1114111. 1114111.0000000002 0x1.0FFFFp+20. !=. 1114111000000000117E-12. 1. 1114111. 1114111.0000000002

0x1.0FFFFp+20. >. 1114111000000000117E-12. 0. 1114111. 1114111.0000000002 0x1.0FFFFp+20. >=. 1114111000000000117E-12. 0. 1114111. 1114111.0000000002 0x1.0FFFFp+20. <=. 1114111000000000117E-12. 1. 1114111. 1114111.0000000002 0x1.0FFFFp+20. <. 1114111000000000117E-12. 1. 1114111. 1114111.0000000002

0x1.0FFFFp+19. <>. 11141110000000000e-10. . 1. 557055.5. 1114111
0x1.0FFFFp+19. ==. 11141110000000000e-10. . 0. 557055.5. 1114111
0x1.0FFFFp+19. !=. 11141110000000000e-10. . 1. 557055.5. 1114111

0x1.0FFFFp+19. >. 11141110000000000e-10. . 0. 557055.5. 1114111
0x1.0FFFFp+19. >=. 11141110000000000e-10. . 0. 557055.5. 1114111
0x1.0FFFFp+19. <=. 11141110000000000e-10. . 1. 557055.5. 1114111
0x1.0FFFFp+19. <. 11141110000000000e-10. . 1. 557055.5. 1114111

** the relational operator "<>" is treated as NOT_EQUAL "!=" even though it's not part of awk syntax

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