Slice

rascal-0.34.0

Synopsis

Assign to a slice of a list or string.

Syntax

• Assignable [ Exp₁ .. Exp3_ ] = Exp₄
• Assignable [ Exp₁, Exp₂ .. Exp₃ ] = Exp₄

Exp₁ and Exp₃ are optional

Description

A slice assignment is defined for List, String and Node and aims to replace a slice from the old value of the assignable by a new value. See Slice, Slice or Slice for a more detailed explanation of slicing.

Let V be the current value of Assignable.

• Assignable [ Exp₁ .. Exp₃ ] = Exp₄: The slice [ Exp₁ .. Exp₃ ] determines two indices begin (inclusive) and end
  (exclusive) in V. A new value V' is computed that is a copy of V but with all the elements in V with begin <= index < end replaced by the elements of the value of Exp₄. Note that the size of V and V' may differ. V' is assigned to the Assignable.

• Assignable [ Exp₁, Exp₂ .. Exp₃ ] = Exp₄: The slice [ Exp₁, Exp₂ .. _Exp₃ ] determines two indices begin (inclusive) and end (exclusive) and a step between indices in V. A new value V' is computed that is a copy of V but with all the elements in V with indices begin, begin+step. ... end-step <= index < end replaced by the successive elements of the value of Exp₄. Note that the size of V and V' may differ. V' is assigned to the Assignable. If the number of indices in the slice and the number of elements in the value of Exp₄ is not equal the following is done:

  • If the number of elements in the slice is larger: the elements of Exp₄ are used in a circular manner.
  • If the number of elements in the slice is smaller: the remaining elements of Exp₄ is inserted after the last index in the slice.

Examples

Replace the elements with index 3, 4, 5 in L:

rascal>L = [0,1,2,3,4,5,6,7,8,9];
list[int]: [0,1,2,3,4,5,6,7,8,9]
rascal>L[3..6] = [100,200,300,400,500];
list[int]: [0,1,2,100,200,300,400,500,6,7,8,9]

Replace the elements with index 1, 3, 5, 7 in L (note how the elements from [100,200] are used in a circular way):

rascal>L = [0,1,2,3,4,5,6,7,8,9];
list[int]: [0,1,2,3,4,5,6,7,8,9]
rascal>L[1,3..8] = [100,200];
list[int]: [0,100,2,200,4,100,6,200,8,9]

Replace the elements with index 1, 3, 5, 7 in L (note how the unused elements from [100,200,300,400,500] are insert at index 7):

rascal>L = [0,1,2,3,4,5,6,7,8,9];
list[int]: [0,1,2,3,4,5,6,7,8,9]
rascal>L[1,3..8] = [100,200,300,400,500];
list[int]: [0,100,2,200,4,300,6,400,500,8,9]

Similar examples for slicing assignment on strings:

rascal>S = "abcdefghij";
str: "abcdefghij"
---
abcdefghij
---
rascal>S[3..6] = "UVWXYZ";
str: "abcUVWXYZghij"
---
abcUVWXYZghij
---
rascal>S = "abcdefghij";
str: "abcdefghij"
---
abcdefghij
---
rascal>S[1,3..8] = "XY";
str: "aXcYeXgYij"
---
aXcYeXgYij
---
rascal>S = "abcdefghij";
str: "abcdefghij"
---
abcdefghij
---
rascal>S[1,3..8] = "UVWXYZ";
str: "aUcVeWgXYZij"
---
aUcVeWgXYZij
---

Replace the elements with index 3, 4, 5 in node N:

rascal>N = "f"(0,true,2,"abc",4,5.5,6,{7,77},8,{9,99,999});
node: "f"(
  0,
  true,
  2,
  "abc",
  4,
  5.5,
  6,
  {7,77},
  8,
  {999,9,99})
rascal>N[3..6] = [100,200,300,400,500];
node: "f"(
  0,
  true,
  2,
  100,
  200,
  300,
  400,
  500,
  6,
  {7,77},
  8,
  {999,9,99})

Replace the elements with index 1, 3, 5, 7 in L (note how the elements from [100,200] are used in a circular way):

rascal>N = "f"(0,true,2,"abc",4,5.5,6,{7,77},8,{9,99,999});
node: "f"(
  0,
  true,
  2,
  "abc",
  4,
  5.5,
  6,
  {7,77},
  8,
  {999,9,99})
rascal>N[1,3..8] = [100,200];
node: "f"(
  0,
  100,
  2,
  200,
  4,
  100,
  6,
  200,
  8,
  {999,9,99})

Replace the elements with index 1, 3, 5, 7 in L (note how the unused elements from [100,200,300,400,500] are insert at index 7):

rascal>N = "f"(0,true,2,"abc",4,5.5,6,{7,77},8,{9,99,999});
node: "f"(
  0,
  true,
  2,
  "abc",
  4,
  5.5,
  6,
  {7,77},
  8,
  {999,9,99})
rascal>N[1,3..8] = [100,200,300,400,500];
node: "f"(
  0,
  100,
  2,
  200,
  4,
  300,
  6,
  400,
  500,
  8,
  {999,9,99})