Difference between revisions of "Slice"

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{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
! Parameter Name !! Default Value !! Meaning
+
! Parameter Name !! Type !! Meaning
 
|-
 
|-
 
| ''seq'' || string or list || sequence to get a subsequence of
 
| ''seq'' || string or list || sequence to get a subsequence of
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| ''to'' || number, optional || 0-based index of first element to *not* include in the result (if negative, count from the end; if omitted, return the rest of the sequence)
 
| ''to'' || number, optional || 0-based index of first element to *not* include in the result (if negative, count from the end; if omitted, return the rest of the sequence)
 
|}
 
|}
 +
 +
== Usage Notes ==
 +
 +
The ''from'' and ''to'' indexes are automatically limited to the range of the sequence; they never cause an Index Error.  This provides for a useful idiom: to get element ''i'' of a sequence, or an empty value if sequence is too short to have such an element, use <c>seq[i:i+1]</c>.  This differs from <c>seq[i]</c> in that the latter will result in an Index Error if ''i'' is out of range.
  
 
== Example ==
 
== Example ==
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<ms>slice("Hello", -2)              // returns "lo"
 
<ms>slice("Hello", -2)              // returns "lo"
 
"Hello"[-2:]                    // equivalent to the above
 
"Hello"[-2:]                    // equivalent to the above
 +
 +
slice("x", -2)                  // returns "x"
 +
"x"[-2:]                        // equivalent to the above
  
 
slice([10,20,30,40,50], 1, 3)  // returns [20, 30]
 
slice([10,20,30,40,50], 1, 3)  // returns [20, 30]

Latest revision as of 20:11, 6 May 2024

slice returns a subset of a string or list. This is equivalent to using the square-brackets slice operator seq[from:to], but with ordinary function syntax.


Arguments

Parameter Name Type Meaning
seq string or list sequence to get a subsequence of
from number, default 0-based index to the first element to return (if negative, counts from the end)
to number, optional 0-based index of first element to *not* include in the result (if negative, count from the end; if omitted, return the rest of the sequence)

Usage Notes

The from and to indexes are automatically limited to the range of the sequence; they never cause an Index Error. This provides for a useful idiom: to get element i of a sequence, or an empty value if sequence is too short to have such an element, use seq[i:i+1]. This differs from seq[i] in that the latter will result in an Index Error if i is out of range.

Example

slice("Hello", -2)              // returns "lo"
"Hello"[-2:]                    // equivalent to the above

slice("x", -2)                  // returns "x"
"x"[-2:]                        // equivalent to the above

slice([10,20,30,40,50], 1, 3)   // returns [20, 30]
[10,20,30,40,50][1:3]           // equivalent to the above