RetroBBS - comp.lang.awk - Re: Is it possible to convert strings to math operators?

Is it possible to convert strings to math operators?

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From: someone@invalid.invalid (someone)
Newsgroups: comp.lang.awk
Subject: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 08:02:31 -0700
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by: someone - Thu, 16 Feb 2023 15:02 UTC

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?

Re: Is it possible to convert strings to math operators?

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From: gazelle@shell.xmission.com (Kenny McCormack)
Newsgroups: comp.lang.awk
Subject: Re: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 15:36:59 -0000 (UTC)
Organization: The official candy of the new Millennium
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by: Kenny McCormack - Thu, 16 Feb 2023 15:36 UTC

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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Re: Is it possible to convert strings to math operators?

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From: someone@invalid.invalid (someone)
Newsgroups: comp.lang.awk
Subject: Re: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 09:20:07 -0700
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by: someone - Thu, 16 Feb 2023 16:20 UTC

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.

Re: Is it possible to convert strings to math operators?

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From: gazelle@shell.xmission.com (Kenny McCormack)
Newsgroups: comp.lang.awk
Subject: Re: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 16:47:08 -0000 (UTC)
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by: Kenny McCormack - Thu, 16 Feb 2023 16:47 UTC

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

Re: Is it possible to convert strings to math operators?

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From: mortonspam@gmail.com (Ed Morton)
Newsgroups: comp.lang.awk
Subject: Re: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 13:16:36 -0600
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by: Ed Morton - Thu, 16 Feb 2023 19:16 UTC

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.

Re: Is it possible to convert strings to math operators?

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Newsgroups: comp.lang.awk
Subject: Re: Is it possible to convert strings to math operators?
Date: Thu, 16 Feb 2023 18:52:59 -0700
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by: someone - Fri, 17 Feb 2023 01:52 UTC

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!

Re: Is it possible to convert strings to math operators?

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Subject: Re: Is it possible to convert strings to math operators?
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by: Kpop 2GM - Wed, 8 Mar 2023 20:44 UTC

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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devel / comp.lang.awk / Re: Is it possible to convert strings to math operators?

Subject	Author
Is it possible to convert strings to math operators?	someone
Re: Is it possible to convert strings to math operators?	Kenny McCormack
Re: Is it possible to convert strings to math operators?	someone
Re: Is it possible to convert strings to math operators?	Kenny McCormack
Re: Is it possible to convert strings to math operators?	Ed Morton
Re: Is it possible to convert strings to math operators?	someone
Re: Is it possible to convert strings to math operators?	Kpop 2GM