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Thus ⎕CT is not used as an absolute value in comparisons, but rather specifies a relative value that is dependent on the magnitude of the number with the greater magnitude. It then follows that ⎕CT has no effect when either of the numbers is zero.
⎕CT may be assigned any value in the range from 0 to 2*¯32 (about 2.3E¯10). A value of 0 ensures exact comparison. The value in a clear workspace is 1E¯14.
⎕CT and ⎕DCT are implicit arguments of the monadic primitive functions Ceiling (⌈), Floor (⌊) and Unique (∪), and of the dyadic functions Equal (=), Excluding (~), Find (⍷), Greater (>), Greater or Equal (≥), Greatest Common Divisor (∨), Index of (⍳), Intersection (∩), Less (<), Less or Equal (≤), Lowest Common Multiple (∧), Match (≡), Membership (∊), Not Match (≢), Not Equal (≠), Residue (|) and Union (∪), as well as ⎕FMT O-format.
⎕CT←1E¯10 1.00000000001 1.0000001 = 1 1 0