System Settings

Settings Affecting Behaviour of Primitive Functions

Name	Description
⎕CT	Comparison Tolerance
⎕DCT	Decimal Comp Tolerance
⎕DIV	Division Method
⎕FR	Floating-Point Representation
⎕IO	Index Origin
⎕ML	Migration Level
⎕PP	Print Precision
⎕RL	Random Link

The following table describes the dependencies that exist between functions, operators and these system variables.

Table 1: Implicit Arguments

System Variable	Monadic Functions	Dyadic Functions	Operators
⎕CT, ⎕DCT	⌈ ⌊ ∪	~ < ≤ = ≥ > ≠ ≡ ≢ ⍳ ∊ ∪ ∩ ⍷ | ∨ ∧	⌸
⎕DIV	÷	÷
⎕FR   ⍝ 1	÷ * ⍟ ! ○ ⌹	+ - × ÷ * ⍟ | ! ○ ∨ ∧ ⊥ ⊤ ⌹
⎕FR   ⍝ 2	⌈ ⌊ ∪	~ < ≤ = ≥ > ≠ ≡ ≢ ⍳ ∊ ∪ ∩ ⍷	⌸
⎕FR   ⍝ 3	⍒ ⍋	⌈ ⌊ ⍒ ⍋ ⍸
⎕IO	⍳ ? ⍒ ⍋ ⍸	⍳ ? ⍒ ⍋ ⍉ ⊃ ⌷ ⍸	⌸ @ []
⎕ML	∊ ↑ ⊃ ≡
⎕PP	⍕
⎕RL	?	?

where, for ⎕FR, 1 indicates functions that compute real numbers and whose precision depends on ⎕FR, 2 indicates functions that perform tolerant comparisons and 3 indicates functions that perform tolerant comparisons.

Note

Tolerant comparisons depend on ⎕FR to select which of ⎕CT and ⎕DCT is used; ⎕FR also determines the precision of the comparison computation that can affect results. However, even primitives involving intolerant comparison (including the tolerant ones with all comparison tolerances set to 0) can depend on ⎕FR if the argument contains DECFs. This is because DECFs must be converted to doubles for comparison. If two DECFs are different but correspond to the same double, then they will be treated as intolerantly unequal when ⎕FR is 1287 but equal when it is 645.