docs

README.md

@@ -26,7 +26,7 @@ console.log(length);
 
 ## API
 
-### `function rollLength(h: number, d0: number, d1: number): number`
+### `function rollLength(h: number, d0: number, d1: number): number | undefined`
 
 Calculates length of a roll (2D spiral).
 
@@ -44,7 +44,7 @@ console.log(length);
 //=> 39.27313461871492
 ```
 
-### `function rollOuterDiameter(h: number, d0: number, l: number, maxIter?: number): number`
+### `function rollOuterDiameter(h: number, d0: number, l: number, maxIter?: number): number | undefined`
 
 Calcuates the outer diameter of a roll (2D spiral).
 
@@ -60,7 +60,7 @@ console.log(outerDiameter);
 //=> 3.0000000000272684
 ```
 
-### `function rollInnerDiameter(h: number, d1: number, l: number): number`
+### `function rollInnerDiameter(h: number, d1: number, l: number): number | undefined`
 
 Calculates the inner diameter of a roll (2D spiral).
 
@@ -76,7 +76,7 @@ console.log(innerDiameter);
 //=> 1.999999999959101
 ```
 
-### `rollMaterialHeight(d0: number, d1: number, l: number): number`
+### `rollMaterialHeight(d0: number, d1: number, l: number): number | undefined`
 
 Calculates the nominal material height or thickness in a roll (2D Spiral).
 
@@ -96,3 +96,21 @@ const materialHeight = rollMaterialHeight(innerDiameter, outerDiameter, length);
 console.log(materialHeight);
 //=> 0.09999178458720241
 ```
+
+### `function rollSolve(h?: number, d0?: number, d1?: number, l?: number): number | undefined`
+
+Solves one missing dimension of a roll (2D spiral).
+
+Pass in at least three arguments to solve for the fourth.
+
+```js
+import { rollSolve } from 'roll-calc';
+
+const materialHeight = 0.06;
+const innerDiameter = 18;
+const outerDiameter = 60;
+const length = rollSolve(materialHeight, innerDiameter, outerDiameter, undefined);
+
+console.log(length);
+//=> 42882.74547004675
+```