Table of Contents

• 1. maxlength
  • 1.1. Syntax
  • 1.2. Stack Effects
  • 1.3. Description
  • 1.4. PostScript Level
  • 1.5. Examples
  • 1.6. Common Use Cases
    • 1.6.1. Pre-allocation Check
    • 1.6.2. Memory Planning
    • 1.6.3. Dictionary Debugging
  • 1.7. Common Pitfalls
  • 1.8. Error Conditions
  • 1.9. Implementation Notes
  • 1.10. Capacity vs. Usage
  • 1.11. See Also

1. maxlength

Returns the maximum capacity of a dictionary.

1.1. Syntax

dict maxlength → int

1.2. Stack Effects

Table 1. Before

Level	Object
0	dict (dictionary)

Table 2. After

Level	Object
0	int (maximum capacity)

1.3. Description

maxlength returns the capacity of dict - the maximum number of key-value pairs it can hold using the VM currently allocated to it.

Level 1: Returns the int operand originally passed to dict - the dictionary’s fixed maximum capacity.

Level 2: Returns the current capacity, which may be larger than the original size if the dictionary has grown.

1.4. PostScript Level

Level 1 and later

1.5. Examples

Basic capacity query

/mydict 5 dict def
mydict length     % Returns 0 (empty)
mydict maxlength  % Returns 5 (capacity)

Dictionary growth (Level 2)

2 dict begin
  /k1 1 def
  /k2 2 def
  /k3 3 def  % Auto-expands in Level 2
  currentdict maxlength  % Returns > 2
end

Checking available space

mydict dup maxlength
exch length sub  % Available slots

1.6. Common Use Cases

1.6.1. Pre-allocation Check

dict dup maxlength exch length sub
requiredSlots lt {
  % Need bigger dictionary
  dup length requiredSlots add dict
  copy
} if

1.6.2. Memory Planning

/estimateMemory {
  dict maxlength 20 mul  % Rough estimate: 20 bytes per entry
} def

1.6.3. Dictionary Debugging

/dictInfo {
  dup length =only ( / ) print
  maxlength =only ( entries\n) print
} def

1.7. Common Pitfalls

maxlength ≠ length - maxlength is capacity, length is current count.

5 dict
dup length     % 0 (no entries yet)
maxlength      % 5 (capacity)

Level Differences - Behavior differs between Level 1 and 2:

% Level 1: Fixed at creation
% Level 2: Can grow (returns current capacity)

Don’t Rely on Exact Values - In Level 2, maxlength may increase unpredictably due to automatic expansion.

1.8. Error Conditions

Error	Condition
[invalidaccess]	Dictionary has no-access attribute
[stackunderflow]	No operand on stack
[typecheck]	Operand is not a dictionary

1.9. Implementation Notes

Level 1: * Returns fixed capacity set at creation * Never changes * Simple field lookup

Level 2: * Returns current allocated capacity * May be larger than original size * Capacity increases in chunks when dictionary grows

1.10. Capacity vs. Usage

Measurement	Operator	Meaning
Current entries	length	Number of key-value pairs
Maximum capacity	maxlength	Slots available with current VM allocation
Available space	maxlength length sub	Remaining capacity (Level 1)

1.11. See Also

• length - Get current entry count

• dict - Create dictionary with initial capacity

• def - Add entry to dictionary

• known - Check if key exists