String slicing and indexing in Ruby - Step-by-Step Execution

Concept Flow - String slicing and indexing

Start with a string

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Choose index or range

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Extract character(s)

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Return substring or character

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Use result or end

This flow shows how Ruby takes a string, uses an index or range to slice, and returns the selected part.

Execution Sample

Ruby

str = "hello"
char = str[1]
slice = str[1..3]
puts char
puts slice

This code extracts a single character and a substring from 'hello' and prints them.

Execution Table

Step	Expression	Evaluation	Result	Explanation
1	str = "hello"	Assign string	"hello"	Variable str now holds 'hello'
2	char = str[1]	Index 1	"e"	Second character is 'e' (indexing starts at 0)
3	slice = str[1..3]	Range 1 to 3	"ell"	Substring from index 1 to 3 inclusive is 'ell'
4	puts char	Print char	e	Outputs 'e' to console
5	puts slice	Print slice	ell	Outputs 'ell' to console
6	End	No more code	Execution stops	Program ends after printing

💡 All code lines executed; program ends normally.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
str	nil	"hello"	"hello"	"hello"	"hello"
char	nil	nil	"e"	"e"	"e"
slice	nil	nil	nil	"ell"	"ell"

Key Moments - 2 Insights

Why does str[1] return 'e' and not 'h'?

Ruby strings start indexing at 0, so str[0] is 'h' and str[1] is the next character 'e'. See execution_table row 2.

What does str[1..3] include exactly?

The range 1..3 includes indexes 1, 2, and 3, so it extracts characters at those positions: 'e', 'l', and 'l'. See execution_table row 3.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of char after step 2?

A "e"

B "h"

C "l"

D "o"

💡 Hint

Check execution_table row 2 under Result column.

At which step does the variable slice get its value?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at execution_table rows and see when slice is assigned.

If we change str[1..3] to str[2..4], what would slice be?

A "ell"

B "llo"

C "hel"

D "lo"

💡 Hint

Check variable_tracker for slice and think about indexes 2 to 4 in 'hello'.

Concept Snapshot

Ruby strings use zero-based indexing.
Use str[index] to get one character.
Use str[start..end] to get substring including end.
Negative indexes count from end.
Out-of-range indexes return nil.
Slicing returns a new string.

Full Transcript

This example shows how Ruby strings can be sliced and indexed. We start with a string 'hello'. Using str[1] gets the character at index 1, which is 'e' because indexing starts at zero. Using str[1..3] extracts characters from index 1 to 3 inclusive, resulting in 'ell'. The program prints these values. Variables str, char, and slice change as the code runs. Understanding zero-based indexing and inclusive ranges helps avoid confusion. The execution table and variable tracker show each step clearly.