Sequence 7 January 2019 OSU CSE 1 Sequence The Sequence - - PowerPoint PPT Presentation

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Sequence 7 January 2019 OSU CSE 1 Sequence The Sequence - - PowerPoint PPT Presentation

Jan 12, 2024 146 likes •537 views

Sequence 7 January 2019 OSU CSE 1 Sequence The Sequence component family allows you to manipulate strings of entries of any (arbitrary) type through direct access by position, similar to an array Another generic type like Queue and Set

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SLIDE 1

Sequence

7 January 2019 OSU CSE 1

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SLIDE 2

Sequence

  • The Sequence component family allows

you to manipulate strings of entries of any (arbitrary) type through direct access by position, similar to an array

– Another generic type like Queue and Set – One possible best practice alternative to the built-in Java array, from the OSU CSE components

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SLIDE 3

Interfaces and Classes

Sequence- Kernel extends Standard extends

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Sequence Sequence1L implements implements Sequence2L Sequence3

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SLIDE 4

Interfaces and Classes

Sequence- Kernel extends Standard extends

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Sequence Sequence1L implements implements Sequence2L Sequence3 Standard has contracts for three methods: clear newInstance transferFrom

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SLIDE 5

Interfaces and Classes

Sequence- Kernel extends Standard extends

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Sequence Sequence1L implements implements Sequence2L Sequence3 SequenceKernel has contracts for three methods: add remove length

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SLIDE 6

Interfaces and Classes

Sequence- Kernel extends Standard extends

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Sequence Sequence1L implements implements Sequence2L Sequence3 Sequence has contracts for six other methods: entry replaceEntry append flip insert extract

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SLIDE 7

Mathematical Model

  • The value of a Sequence variable is

modeled as a string of entries of type T

  • Formally:

type Sequence is modeled by string of T

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SLIDE 8

No-argument Constructor

  • Ensures:

this = < >

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SLIDE 9

Example

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Code State

Sequence<Integer> si = new Sequence1L<>();

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SLIDE 10

Example

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Code State

Sequence<Integer> si = new Sequence1L<>(); si = < >

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SLIDE 11

add

void add(int pos, T x)

  • Adds x at position pos of this.
  • Aliases: reference x
  • Updates: this
  • Requires:

0 <= pos and pos <= |this|

  • Ensures:

this = #this[0, pos) * <x> * #this[pos, |#this|)

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SLIDE 12

Example

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Code State

si = < 49, 3 > z = 70 si.add(1, z);

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SLIDE 13

Example

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Code State

si = < 49, 3 > z = 70 si.add(1, z); si = < 49, 70, 3 > z = 70

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SLIDE 14

Example

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Code State

si = < 49, 3 > z = 70 si.add(1, z); si = < 49, 70, 3 > z = 70 Note the alias created here, which you cannot see in the tracing table; you should be able to draw the appropriate diagram showing it.

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SLIDE 15

remove

T remove(int pos)

  • Removes and returns the entry at position pos
  • f this.
  • Updates: this
  • Requires:

0 <= pos and pos < |this|

  • Ensures:

this = #this[0, pos) * #this[pos+1, |#this|) and <remove> = #this[pos, pos+1)

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SLIDE 16

Example

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Code State

si = < 49, 3, 70 > z = –584 z = si.remove(1);

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SLIDE 17

Example

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Code State

si = < 49, 3, 70 > z = –584 z = si.remove(1); si = < 49, 70 > z = 3

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SLIDE 18

length

int length()

  • Reports the length of this.
  • Ensures:

length = |this|

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SLIDE 19

entry

T entry(int pos)

  • Reports the entry at position pos of this.
  • Aliases: reference returned by entry
  • Requires:

0 <= pos and pos < |this|

  • Ensures:

<entry> = this[pos, pos+1)

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SLIDE 20

Example

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Code State

si = < 49, 3, 70 > z = –584 z = si.entry(1);

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SLIDE 21

Example

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Code State

si = < 49, 3, 70 > z = –584 z = si.entry(1); si = < 49, 3, 70 > z = 3

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SLIDE 22

Example

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Code State

si = < 49, 3, 70 > z = –584 z = si.entryAt(1); si = < 49, 3, 70 > z = 3 Note the alias created here, which you cannot see in the tracing table; you should be able to draw the appropriate diagram showing it.

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SLIDE 23

replaceEntry

T replaceEntry(int pos, T x)

  • Replaces the entry at position pos of this with x, and

returns the old entry at that position.

  • Aliases: reference x
  • Updates: this
  • Requires:

0 <= pos and pos < |this|

  • Ensures:

this = #this[0, pos) * <x> * #this[pos+1, |#this|) and <replaceEntry> = #this[pos, pos+1)

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SLIDE 24

Example

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Code State

si = < 49, 70 > z = –8 w = -584 w = si.replaceEntry(1, z);

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SLIDE 25

Example

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Code State

si = < 49, 70 > z = –8 w = -584 w = si.replaceEntry(1, z); si = < 49, -8 > z = –8 w = 70

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SLIDE 26

Example

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Code State

si = < 49, 70 > z = –8 w = -584 w = si.replaceEntryAt(1, z); si = < 49, -8 > z = –8 w = 70

Note the alias created here, which you cannot see in the tracing table; you should be able to draw the appropriate diagram showing it.

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SLIDE 27

Another Example

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Code State

si = < 49, 70 > z = –8 z = si.replaceEntry(1, z);

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SLIDE 28

Another Example

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Code State

si = < 49, 70 > z = –8 z = si.replaceEntry(1, z); si = < 49, -8 > z = 70

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SLIDE 29

Another Example

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Code State

si = < 49, 70 > z = –8 z = si.replaceEntry(1, z); si = < 49, -8 > z = 70

This use of the method avoids creating an alias: it swaps z with the entry previously at position 1.

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SLIDE 30

append

void append(Sequence<T> s)

  • Concatenates (“appends”) s to the end of

this.

  • Updates: this
  • Clears: s
  • Ensures:

this = #this * #s

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SLIDE 31

flip

void flip()

  • Reverses (“flips”) this.
  • Updates: this
  • Ensures:

this = rev(#this)

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SLIDE 32

insert

void insert(int pos, Sequence<T> s)

  • Inserts s at position pos of this, and clears s.
  • Updates: this
  • Clears: s
  • Requires:

0 <= pos and pos <= |this|

  • Ensures:

this = #this[0, pos) * #s * #this[pos, |#this|)

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SLIDE 33

Example

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Code State

si1 = < 8, 6, 92 > si2 = < 1, -7 > si1.insert(2, si2);

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SLIDE 34

Example

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Code State

si1 = < 8, 6, 92 > si2 = < 1, -7 > si1.insert(2, si2); si1 = < 8, 6, 1, -7, 92 > si2 = < >

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SLIDE 35

extract

void extract(int pos1, int pos2, Sequence<T> s)

  • Removes the substring of this starting at position pos1 and

ending at position pos2-1, and puts it in s.

  • Updates: this
  • Replaces: s
  • Requires:

0 <= pos1 and pos1 <= pos2 and pos2 <= |this|

  • Ensures:

this = #this[0, pos1) * #this[pos2, |#this|) and s = #this[pos1, pos2)

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SLIDE 36

Example

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Code State

si1 = < 8, 6, 92, 27, 0 > si2 = < 1, -7, 562 > si1.extract(1, 3, si2);

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SLIDE 37

Example

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Code State

si1 = < 8, 6, 92, 27, 0 > si2 = < 1, -7, 562 > si1.extract(1, 3, si2); si1 = < 8, 27, 0 > si2 = < 6, 92 >

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SLIDE 38

Resources

  • OSU CSE Components API: Sequence

– http://cse.osu.edu/software/common/doc/

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