Infix functions for readable calls in Kotlin - Step-by-Step Execution

Concept Flow - Infix functions for readable calls

Define infix function

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Call function with infix syntax

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Function executes with passed argument

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Return result or perform action

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Use result or continue program

An infix function is defined with the 'infix' keyword and called without dots or parentheses for cleaner, readable code.

Execution Sample

Kotlin

infix fun Int.times(str: String) = str.repeat(this)

val result = 3 times "Hi "
println(result)

Defines an infix function 'times' to repeat a string multiple times and calls it in a readable way.

Execution Table

Step	Action	Evaluation	Result
1	Define infix function 'times'	Int.times(String) = String repeated Int times	Function ready
2	Call '3 times "Hi "'	3.times("Hi ")	Calls function with this=3, str="Hi "
3	Inside function: str.repeat(this)	"Hi ".repeat(3)	"Hi Hi Hi "
4	Assign result	result = "Hi Hi Hi "	Variable 'result' holds "Hi Hi Hi "
5	Print result	println(result)	Output: Hi Hi Hi
6	End	Program ends	Execution complete

💡 Function call completes and program ends after printing the repeated string.

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
result	undefined	undefined	"Hi Hi Hi "	"Hi Hi Hi "

Key Moments - 3 Insights

Why can we call the function without dots or parentheses?

Because the function is marked with 'infix', Kotlin allows calling it using infix notation as shown in step 2 of the execution_table.

What does 'this' refer to inside the infix function?

'this' refers to the integer on which the function is called, here it is 3 as shown in step 3 of the execution_table.

Can any function be called with infix notation?

No, only functions with a single parameter and marked with the 'infix' keyword can be called this way, as shown in step 1.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the value of 'this' inside the function?

A result

B "Hi "

C 3

D undefined

💡 Hint

Check the 'Evaluation' column at step 3 where 'this' is used as the repeat count.

At which step does the variable 'result' get its value assigned?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Action' column for assignment to 'result' in the execution_table.

If the function was not marked 'infix', how would the call change?

A 3 times "Hi "

B 3.times("Hi ")

C "Hi ".repeat(3)

D times(3, "Hi ")

💡 Hint

Without 'infix', Kotlin requires dot and parentheses syntax as in step 2.

Concept Snapshot

infix fun <Type>.functionName(param: ParamType) = ...
Call with: value functionName argument
Only single parameter functions can be infix.
Improves readability by removing dots and parentheses.
Useful for DSLs and expressive code.

Full Transcript

This visual execution shows how Kotlin infix functions work. First, an infix function 'times' is defined to repeat a string a number of times. Then it is called using infix syntax without dots or parentheses. Inside the function, 'this' refers to the integer 3. The string "Hi " is repeated 3 times, producing "Hi Hi Hi ". This result is assigned to the variable 'result' and printed. The program ends after printing. Key points are that infix functions must have one parameter and be marked with 'infix' to allow this readable call style.