LFE-Specific Conveniences

LFE provides several forms that make working with maps more pleasant than it has any right to be:

The (map) Constructor

(map 'a 1 'b 2 'c 3)
#M(a 1 b 2 c 3)

The (mref Map Key) Function

Safely access values with optional defaults:

(mref '#M(a 1 b 2) 'a)
1

(mref '#M(a 1 b 2) 'z 'default)
default

The (mset Map Key Value) Function

Update or add a key-value pair:

(mset '#M(a 1 b 2) 'c 3)
#M(a 1 b 2 c 3)

The (mupd Map Key Value) Function

Update an existing key (fails if key doesn’t exist):

(mupd '#M(a 1 b 2) 'a 42)
#M(a 42 b 2)

The (map-get Map Key) Macro

Pattern matching extraction in let bindings:

(let (((map-get '#M(a 1 b 2) a val)))
  val)
1