Dictionary in Smalltalk

Keys to values, with at:ifAbsent: reading safely.

"Dictionary maps keys to values; at:ifAbsent: reads safely."
| prices |
prices := Dictionary new.
prices at: 'broadside' put: 120.
prices at: 'chapbook' put: 340.
prices at: 'bookmark' put: 15.

Transcript show: (prices at: 'chapbook') printString; cr.
Transcript show: (prices at: 'poster' ifAbsent: [0]) printString; cr.

prices keysAndValuesDo: [:job :cents |
    Transcript show: job, ' -> ', cents printString; cr].

Transcript show: prices keys asSortedCollection printString; cr.

How it works

1. at:put: writes; at: reads and raises on a miss.
2. at:ifAbsent: supplies a block for the missing case.
3. keysAndValuesDo: walks both halves at once.

Keywords and builtins used here

• Dictionary
• Transcript
• asSortedCollection
• cr
• keys
• new
• printString

The run, in numbers

Lines

14

Characters to type

482

Tokens

82

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 82 seconds.

Type this snippet

Step 2 of 4 in Collections, step 11 of 31 in Language basics.

← Previous Next →