Conditionals in Smalltalk

No if statement: booleans take ifTrue:ifFalse: messages.

"No if statement: booleans take ifTrue:ifFalse: messages."
| paperLeft job |
paperLeft := 42.

paperLeft > 100
    ifTrue: [Transcript show: 'Run the full edition'; cr]
    ifFalse: [Transcript show: 'Proofs only today'; cr].

"The whole thing is an expression that answers a value."
job := paperLeft > 40
    ifTrue: ['chapbook']
    ifFalse: ['bookmark'].
Transcript show: 'Next up: ', job; cr.

(paperLeft between: 40 and: 50)
    ifTrue: [Transcript show: 'Order more stock'; cr].

How it works

1. The condition object receives the branching message.
2. Both branches are blocks; the chosen one runs.
3. The whole send is an expression that answers a value.

Keywords and builtins used here

• Transcript
• cr

The run, in numbers

Lines

16

Characters to type

464

Tokens

67

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 67 seconds.

Type this snippet

Step 1 of 3 in Control flow, step 7 of 31 in Language basics.

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Conditionals in other languages

• C
• R
• Ruby