i and j
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It might have come from FORTRAN, but "i" was also used for short of "index". When using nested loops the next letter was the most obvious ("j", "k", ...) For me personally it makes perfect sense in some way. If you see a one letter variable in code, there is almost a 100% chance that it is a loop variable. Also a one letter loop variable in an array indication (
some_array[i]) is easier readable than (some_array[index]). (though that is perhaps personal taste)V.
(MQOTD rules and previous solutions)
V. wrote:
If you see a one letter variable in code, there is almost a 100% chance that it is a loop variable.
Or you are in QA... :sigh:
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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It might have come from FORTRAN, but "i" was also used for short of "index". When using nested loops the next letter was the most obvious ("j", "k", ...) For me personally it makes perfect sense in some way. If you see a one letter variable in code, there is almost a 100% chance that it is a loop variable. Also a one letter loop variable in an array indication (
some_array[i]) is easier readable than (some_array[index]). (though that is perhaps personal taste)V.
(MQOTD rules and previous solutions)
V. wrote:
loop variable in an array indication (
some_array[i]) is easier readable than (some_array[index]). (though that is perhaps personal taste)It depends if that variable has other meaning / is meant to be stored but yes, I concur.
DURA LEX, SED LEX GCS d--- s-/++ a- C++++ U+++ P- L- E-- W++ N++ o+ K- w+++ O? M-- V? PS+ PE- Y+ PGP t++ 5? X R++ tv-- b+ DI+++ D++ G e++>+++ h--- ++>+++ y+++* Weapons extension: ma- k++ F+2 X If you think 'goto' is evil, try writing an Assembly program without JMP. -- TNCaver When I was six, there were no ones and zeroes - only zeroes. And not all of them worked. -- Ravi Bhavnani
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To add to what the others said about FORTRAN default variable types, variable names were limited to 6 characters as well so short variable names were a good idea. It was a convention that "generic loop counters" were I, J, and K (no lower case in those days, either!) In addition, lines were limited to 80 characters of which the first 6 where for label numbers, used to target lines with GOTO and suchlike flow control; and the seventh was for a "Continuation character" which allowed you to use more than 72 characters in your code statement. Short names were a good idea in those days! :laugh:
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
Short names still are a good idea. As a general rule, I'll use initials for temporary variables in loops etc and as the scope gets greater increase the size and detail of the name.
veni bibi saltavi
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Looking at Marc's early work on the commodore 64 raised the following question? Why do we seem to use i and j for loop variables? Where did it come from I wonder. And no I have not tried to google it!
Never underestimate the power of human stupidity RAH
I was initially going to nod to the FORTRAN crowd, then I thought further back, to linear algebra. Indices in vectors and matrices were traditionally i, j, ... My 2cents. Cheers, Peter
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
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To add to what the others said about FORTRAN default variable types, variable names were limited to 6 characters as well so short variable names were a good idea. It was a convention that "generic loop counters" were I, J, and K (no lower case in those days, either!) In addition, lines were limited to 80 characters of which the first 6 where for label numbers, used to target lines with GOTO and suchlike flow control; and the seventh was for a "Continuation character" which allowed you to use more than 72 characters in your code statement. Short names were a good idea in those days! :laugh:
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Looking at Marc's early work on the commodore 64 raised the following question? Why do we seem to use i and j for loop variables? Where did it come from I wonder. And no I have not tried to google it!
Never underestimate the power of human stupidity RAH
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I was initially going to nod to the FORTRAN crowd, then I thought further back, to linear algebra. Indices in vectors and matrices were traditionally i, j, ... My 2cents. Cheers, Peter
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
The designers of FORTRAN used I,J,...etc. because FORTRAN was designed for FORmula TRANslation and a lot of the language development came from having to process this linear algebra. So when the Integer variables were defined it was natural to use I and J, etc. So which came first the chicken or the egg?
- I would love to change the world, but they won’t give me the source code.
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The designers of FORTRAN used I,J,...etc. because FORTRAN was designed for FORmula TRANslation and a lot of the language development came from having to process this linear algebra. So when the Integer variables were defined it was natural to use I and J, etc. So which came first the chicken or the egg?
- I would love to change the world, but they won’t give me the source code.
There is no chicken/egg debate. I'm saying FORTRAN followed the linear algebra usage.
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
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I was initially going to nod to the FORTRAN crowd, then I thought further back, to linear algebra. Indices in vectors and matrices were traditionally i, j, ... My 2cents. Cheers, Peter
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
For matrices I typically prefer
rowandcolumn. That's still reasonably short, and can help a lot in the readability of some of the matrix operations. (talking of linear algebra matrices here, but you might apply the same reasoning to database tables, resulting in index names likerecordandfield)GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
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There is no chicken/egg debate. I'm saying FORTRAN followed the linear algebra usage.
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
I concur. Tensor algebra is much older than FORTRAN, and they always used i, j, k, l for indices, continuing with m, n, and (rarely) more when needed. Mathematicians are notoriously lazy, so they never waste more than one letter for an index variable. ;)
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
