Re: Missing function for locating string fragment?
Hi Alex, On 12. Sep, 2014, at 16:06, Alexander Burger a...@software-lab.de wrote: It is not a good idea to build a list only to count its length. Better count in a loop directly, e.g.: (de sindex (Frag Src) (for ((I . L) (chop Src) L (cdr L)) (T (pre? Frag L) I) ) ) For this 'sindex' I think it would be good to first test if Frag is NIL, since with your version above (sindex NIL foo) would give 1. Therefor I would do this: (de sindex (Frag Src) (if Frag (for ((I . L) (chop Src) L (cdr L)) (T (pre? Frag L) I) ) ) ) /Jon-- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: Missing function for locating string fragment?
Hi Jon, For this 'sindex' I think it would be good to first test if Frag is NIL, since with your version above (sindex NIL foo) would give 1. The 1 is (arguably) correct, because an empty string is a substring of *every* string. : (pre? NIL bla) - bla ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Missing function for locating string fragment?
Hi, The other day I noticed that I hadn't seen a PicoLisp function for locating a string fragment within a longer string. Is there one that I just have failed to notice? It is quite common for programming languages to have an index function that does this. PicoLisp has an 'index' function, but that one cannot be used like this: (index Li PicoLisp) One way to make up the function I'm missing, could be like this: (de sindex (Frag Src) (if (match (make (link '@A) (mapcar link (chop Frag)) (link '@B)) (chop Src)) (length @A) ) ) Then (sindex Li PicoLisp) would give 4. Maybe it would be preferable for it to give 5. As it is quite common for PicoLisp functions to have different behaviours depending on the type of input, the behaviour of my 'sindex' could also be made a part of the standard PicoLisp 'index' function. /Jon-- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: Missing function for locating string fragment?
Hi Jon, The other day I noticed that I hadn't seen a PicoLisp function for locating a string fragment within a longer string. Is there one that I just have failed to notice? Yes, that's right. In fact, the only functions which I would regard as string manipulations (i.e. operate directly on a symbol name) are pre? sub? uppc lowc This is on purpose. In general, arbitrary manipulations of string data are supposed to be done with the (quite rich) set of List functions (after 'chop'ing the symbol name, for example). This gives much more flexibility and avoids duplicate functionalities. It is quite common for programming languages to have an index function that does this. PicoLisp has an 'index' function, but that one cannot be used like this: (index Li PicoLisp) The above 'sub?' is close to it, but doesn't return a position. One way to make up the function I'm missing, could be like this: (de sindex (Frag Src) (if (match (make (link '@A) (mapcar link (chop Frag)) (link '@B)) (chop Src)) (length @A) ) ) It is not a good idea to build a list only to count its length. Better count in a loop directly, e.g.: (de sindex (Frag Src) (for ((I . L) (chop Src) L (cdr L)) (T (pre? Frag L) I) ) ) Then (sindex Li PicoLisp) would give 4. Maybe it would be preferable for it to give 5. Yes, the above returns 5. This is more in sync with the PicoLisp convention of counting elements from 1. As it is quite common for PicoLisp functions to have different behaviours depending on the type of input, the behaviour of my 'sindex' could also be made a part of the standard PicoLisp 'index' function. I must say that rings an alarm in my head when index numbers are used to operate on lists (or symbol names). Usually there is a better way. What do you need this function for? ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: Missing function for locating string fragment?
Hi Alex, Thanks for the reply, and for suggesting a better solution than the one I made up. I have no immediate use for such a 'sindex' function, and maybe this is not a function that one would need very often when doing things the PicoLisp way. Have a nice weekend! /Jon On 12. sep. 2014, at 16:06, Alexander Burger a...@software-lab.de wrote: Hi Jon, The other day I noticed that I hadn't seen a PicoLisp function for locating a string fragment within a longer string. Is there one that I just have failed to notice? Yes, that's right. In fact, the only functions which I would regard as string manipulations (i.e. operate directly on a symbol name) are pre? sub? uppc lowc This is on purpose. In general, arbitrary manipulations of string data are supposed to be done with the (quite rich) set of List functions (after 'chop'ing the symbol name, for example). This gives much more flexibility and avoids duplicate functionalities. It is quite common for programming languages to have an index function that does this. PicoLisp has an 'index' function, but that one cannot be used like this: (index Li PicoLisp) The above 'sub?' is close to it, but doesn't return a position. One way to make up the function I'm missing, could be like this: (de sindex (Frag Src) (if (match (make (link '@A) (mapcar link (chop Frag)) (link '@B)) (chop Src)) (length @A) ) ) It is not a good idea to build a list only to count its length. Better count in a loop directly, e.g.: (de sindex (Frag Src) (for ((I . L) (chop Src) L (cdr L)) (T (pre? Frag L) I) ) ) Then (sindex Li PicoLisp) would give 4. Maybe it would be preferable for it to give 5. Yes, the above returns 5. This is more in sync with the PicoLisp convention of counting elements from 1. As it is quite common for PicoLisp functions to have different behaviours depending on the type of input, the behaviour of my 'sindex' could also be made a part of the standard PicoLisp 'index' function. I must say that rings an alarm in my head when index numbers are used to operate on lists (or symbol names). Usually there is a better way. What do you need this function for? ♪♫ Alex PԔ � j)mX��� ��zV�u�.n7�
