OpenEuphoria

[tutorial] Basic Sequence Operations

• Posted by _tom (admin) Jan 22, 2019
• 1580 views

Trying some new definitions for properties and functions.

_tom

Sequence Basics

A sequence is "a list of objects." A string is "a flat sequence of integer values."

All of these examples work on oE|Phix (Phix has additional features).

s = { □ , □ , □ , □ }     -- sequence 
str = "●●●●"              -- string 

Subscript notation lets us identify the parts of a sequence: item s[2] , slice s[2..2] , and gap s[2..1] .

      1          2            3     4      -- index values    
s = { □ ,        □         ,  □   , □ } 
           {}   {□} 
         gap      slice 
        s[2..1]   s[2..2]  
 
                 □ 
                  item 
                  s[2] 

The parts of a sequence can be output:

s = { □ ,   ■   , □ , □ } 
 
? s[2] 
    --> ■            -- item 
 
? s[2..2] 
    --> { ■ }        -- slice 
 
? s[2..1] 
    --> {}           -- gap 

You can change the value of an item with an assignment statement.

s = { □ ,   ■   , □ , □ } 
s[2] =      ▧ 
? s 
--> { □ ,   ▧   , □ , □ } 

fill

You can fill a slice with an atom value:

s = { □ ,  ■  , ■ , □ } 
s[2..3] =  ● 
? s 
--> { □ ,  ●  , ● , □ } 

sequence to slice

You can assign items of a sequence to a slice of the same length:

s = { □ ,   ■ , ■   , □ } 
s[2..3] = { ▧ , ▧ } 
? s 
--> { □ ,   ▧ , ▧   , □ } 

remove)

The remove) function "gets rid of an item or slice."

s = { □ ,     ■   , □ , □ } 
s = remove(s, 2 ) 
? s 
--> { □ , □ , □ } 
 
s = { □ ,     ■ , ■ , □ } 
s = remove(s, 2 , 3 ) 
? s 
--> { □ , □  } 

insert)

The insert) function "replaces a gap with one object." The length of the target sequence increases by one.

           -- gap  
           -- s[2..1] 
 
s = { □ ,                 ■ , □ , □ } 
s = insert(s, {▧,▧}, 2 ) 
? s 
--> { □ ,     {▧,▧},      ■ , □ , □ } 

splice)

The splice) function "end to end joins the items of a sequence in a gap." The length of the target sequence increases by the length of the spliced sequence.

            -- gap 
            -- s[2..1] 
 
s = { □ ,                ■ , □ , □ } 
s = splice(s, {▧,▧}, 2 ) 
? s 
--> { □ ,      ▧,▧ ,     ■  , □ , □ } 

replace)

The replace) function "end to end joins the items of a sequence where a slice used to be."

                 -- slice 
                 -- s[2..3] 
 
s = { □ ,              ■ , ■ , □ } 
s = replace(s, {▧,▧,▧}, 2 , 3 ) 
? s 
--> { □ ,          ▧,  ▧,  ▧ , □ } 

The length of the target sequence can change.

                 -- slice 
                 -- s[2..3] 
 
s = { □ ,              ■ , ■ , □ } 
s = replace(s, {▧},     2 , 3 ) 
? s 
--> { □ ,              ▧,     , □ }