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Mathematica > Core Language > Procedural Programming > Looping Constructs > Do >

BUILT-IN MATHEMATICA SYMBOL

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Do

evaluates expr

times.

evaluates expr with the variable i successively taking on the values

through

(in steps of

starts with

uses steps di.

uses the successive values

, ....

evaluates expr looping over different values of j, etc. for each i.

MORE INFORMATION

Do uses the standard Mathematica iteration specification.

You can use Return, Break, Continue, and Throw inside Do.

Unless an explicit Return is used, the value returned by Do is Null.

Do first evaluates spec, then localizes the variable specified and successively assigns values to it, each time evaluating expr.

Do effectively uses Block to localize values or variables.

In Do is effectively equivalent to Do.

EXAMPLES

CLOSE ALL

Basic Examples (2)

Print the first four squares:

n goes from

in steps of

Print the first four squares:

In[1]:=

n goes from

in steps of

In[1]:=

Scope (7)

Evaluate Print

twice:

The step can be negative:

The values can be symbolic:

Loop over i and j, with j running up to i-1:

The body can be a procedure:

Break breaks out of Do:

Continue continues the loop, without executing the rest of the body:

Generalizations & Extensions (1)

Give a list of values to iterate over:

Applications (5)

Generate a symbolic continued fraction:

Build up a list of primes:

Alternatively use Reap and Sow:

Implement backsubstitution:

Implement LU triangular decomposition of matrices:

The selection sort algorithm:

Properties & Relations (1)

Equivalent loops: