# FoldWhile

FoldWhile[f,x,{a1,a2,},test]

returns the first expression f[ f[f[x,a1],a2],ak] to which applying test does not yield True.

FoldWhile[f,list,test]

is equivalent to FoldWhile[f,First[list],Rest[list],test].

FoldWhile[f,x,{a1,a2,},test,m]

supplies the most recent m results as arguments for test at each step.

FoldWhile[f,x,{a1,a2,},test,All]

supplies all results so far as arguments for test at each step.

FoldWhile[f,x,{a1,a2,},test,m,n]

returns the result after applying f an extra n times after test fails.

FoldWhile[f,x,{a1,a2,},test,m,-n]

returns the result found when f had been applied n fewer times.

FoldWhile[f,test]

represents an operator form of FoldWhile that can be applied to expressions.

# Details # Examples

open allclose all

## Basic Examples(3)

Divide 5! by consecutive positive integers, until the result is a non-integer:

Add 1/n6 terms until Unequal yields False for two consecutive results in machine arithmetic:

Divide 5! by consecutive positive integers and return the last integer result:

## Scope(9)

Starting with 12, subtract increasing integers while the remainder is still positive:

Use Echo to display the intermediate results:

Display the results of the corresponding tests:

Compute a random walk starting from the origin, and return the first point whose norm is beyond 10:

Fold Cross over a list of random unit vectors while the norm of the result is larger than 0.1:

Add 1/n8 terms until Unequal yields False for two consecutive results in machine arithmetic:

Add random integers to 0 while all results are different, returning the first value that was repeated:

Divide 5! by consecutive positive integers, returning the first non-integer result:

Return the last integer result:

Return the next-to-last integer result:

Abort the computation before it is finished:

Use FoldWhile in operator form:

FoldWhile admits operator forms of three or four arguments when the third and fourth arguments are explicit integers:

## Properties & Relations(4)

If test[x] does not yield True, FoldWhile[f,x,alist,test] returns x:

FoldWhile[f,x,alist,test,] is equivalent to Last[FoldWhileList[f,x,alist,test,]]:

FoldWhile[f,x,list,True&] is equivalent to Fold[f,x,list]:

FoldWhile[f,x,list,test,m,n] is equivalent to NestWhile[f,x,test,m,Length[list],n] for a function f taking only one argument: