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Function
src/math/math.ts:1571sum
sum(expr: Expression, index: Expression, lower: Expression, upper: Expression): ExpressionComputes a finite summation:
`sum(expr, k, a, b) = Σ_{k=a}^{b} expr`. - If bounds are integers and the number of terms ≤
`Settings.MAX_PRODUCT_AND_SUMMATION_ITERATION`, evaluates by accumulating each term. - If
`lower > upper`, returns
`0`(empty range). - If
`expr`does not depend on the index variable, simplifies to
`expr · (b − a + 1)`. - Otherwise returns a symbolic
`sum(expr, k, a, b)`node.
Parameters
| Name | Type | Description |
|---|---|---|
expr | Expression | The expression to be summed. |
index | Expression | The index variable (must be a plain symbol). |
lower | Expression | The lower bound (integer required for evaluation). |
upper | Expression | The upper bound (integer required for evaluation). |
Returns
Expression — The summation result or a symbolic `sum` node.
Examples
// Σ_{k=1}^{5} k = 15
sum('k', 'k', 1, 5).text() // "15"