38 lines
1.6 KiB
JavaScript
38 lines
1.6 KiB
JavaScript
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import {onType} from '#core/helpers.js'
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import {Returns} from '#core/Type.js'
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import {Optional} from '#core/TypePatterns.js'
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import {boolnum} from './helpers.js'
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import {NumberT} from './NumberT.js'
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// In nanomath, we take the point of view that two comparators are primitive:
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// indistinguishable(a, b, relTol, absTol), and exceeds(a, b). All others
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// are defined generically in terms of these. They typically return BooleanT,
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// but in a numbers-only bundle, they return 1 or 0.
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// Notice a feature of TypedDispatcher: if you specify one tolerance, you must
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// specify both.
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export const indistinguishable = onType(
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[NumberT, NumberT, Optional([NumberT, NumberT])],
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boolnum((a, b, [tolerances = [0, 0]]) => {
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const [relTol, absTol] = tolerances
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if (relTol < 0 || absTol < 0) {
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throw new RangeError(
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`Tolerances (relative: ${relTol}, absolute: ${absTol}) `
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+ 'must be nonnegative')
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}
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if (isNaN(a) || isNaN(b)) return false
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if (a === b) return true
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if (!isFinite(a) || !isFinite(b)) return false
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// |a-b| <= absTol or |a-b| <= relTol*max(|a|, |b|)
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const diff = Math.abs(a-b)
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if (diff <= absTol) return true
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const magnitude = Math.max(Math.abs(a), Math.abs(b))
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return diff <= relTol * magnitude
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})
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)
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// Returns truthy if a (interpreted as completely precise) represents a
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// greater value than b (interpreted as completely precise). Note that even if
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// so, a and b might be indistinguishable() to some tolerances.
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export const exceeds = onType([NumberT, NumberT], boolnum((a, b) => a > b))
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