03_Input_Assistance_eng.srt

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This section of Introduction
to Wolfram Notebooks

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is about notebook features
for entering programs

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and for making programs
more readable.

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As a simple example,

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here is a short program
based on the manipulate function

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and as this program
is being entered,

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mismatched brackets
and incomplete command names

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and anything else that is
even temporarily, a syntax error

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is shown in a different color.

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This particular program gives
a slider for adjusting a parameter

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in an image processing operation.

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A good way to check

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that a program like this
has been entered correctly

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is to look for anything
that is displayed

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in a color other than black.

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Any name that doesn't
have a definition

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is shown in a different color.

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So for example, if the name of
a command is spelled incorrectly,

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like the name in this example,

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that name will be shown
in a different color.

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Color is also used to show
a syntax errors.

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For example, the unmatched
brackets in this input

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are shown in a different color.

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You can use notebook options

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to make the different colors
easier to see.

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For example, here is that
notebook with option settings

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to show local variables,

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like the variable r
in the Manipulate function,

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in bright green,

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undefined names, like
the incomplete name shown here,

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in large underlined
magenta characters;

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and syntax errors,
like unmatched brackets, in red.

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There are several
tools specifically

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to help with getting all
of the brackets and braces

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and other delimiters to match up.

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For example,
when a closing delimiter

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such as a closing bracket
is entered,

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the opening delimiter flashes
briefly to indicate the matching.

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So in this input, as soon as
the closing bracket is entered,

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the opening bracket
flashes briefly

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and the color changes to black.

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Here is that same input

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with the colors
set back to their defaults,

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which again shows the opening
delimiters flashing briefly

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as soon as the closing delimiters
are entered.

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Another way to find
matching brackets

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is to click anywhere
between matching brackets,

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which causes the nearest
enclosing brackets

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to be highlighted.

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A similar feature is the Check
Balance item under the Edit menu.

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Positioning the cursor anywhere
between matching delimiters

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and choosing Check Balance,
or the keyboard shortcut,

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has the effect of selecting
everything between

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and including
the matching delimiters.

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Choosing Check Balance again
expands the selection out

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to the next nearest
enclosing delimiters.

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Another related feature
is repeated clicking,

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which can be used
to select subexpressions.

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For example, double-clicking
the EdgeDetect command,

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selects the command name
and clicking three times

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selects the command

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as well as the arguments
and the enclosing square brackets.

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In this example,
clicking four times

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selects the arguments
of the Manipulate command

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and clicking five or more times
selects the entire input.

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These features for finding
subexpressions

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and matching brackets

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are especially useful for commands
that are many lines long,

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where it can be difficult to locate
the beginning and the end

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of a command.

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There are also several ways
of using formatting

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to help with getting
the syntax right

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and to improve
the readability of programs.

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A traditional method
that has been used

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since the early days
of computer programming

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is indentation.

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For example, that program
could be formatted like this,

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which puts matching delimiters
at similar levels of indentation.

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Another formatting tool

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is conventional
mathematical notation,

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which can be useful
in programs that include

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any sort of mathematics.

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For example, here is an input
to the Erosion function

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where the second argument
is a matrix.

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But rather than showing
the matrix in a linear form,

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with nested curly braces
as in this input,

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that matrix can be shown in
traditional mathematical notation

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by selecting the Cell
and choosing TraditionalForm

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from the Convert To submenu
under the Cell menu,

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which makes that part of the input
more recognizable as a matrix.

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Here is another example,

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this time involving a program
from signal processing.

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A key detail of this program
is this bit of mathematics,

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which is entered here
in linear programming notation,

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but which can be made
more recognizable

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by formatting that formula
as a fraction

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using either StandardForm
or TraditionalForm

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from the Convert To menu.

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One other formatting tool that
can be useful in larger programs,

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especially programs
much larger than this one,

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is to iconize parts
of the program.

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For example, that mathematical
formula can be replaced

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by what is basically
a labeled button

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by using the iconize function.

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The iconize form
can be copied and pasted

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like any other expression,

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and in a program it behaves
just like the original expression.

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You can also iconize
selections in a program.

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For example, in this program
you can triple click the name

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of the plotting function

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to select the part of this program
that generates the plot

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and then choose
Iconize Selection

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under the Edit menu to replace
that selection with an icon.

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There is also a keyboard shortcut
for iconizing a selection,

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and on many platforms
there is a context menu

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for selections
that can be opened,

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typically by ALT clicking or
CONTROL clicking on a selection.

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For example, after selecting part
of the program,

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this shows that context menu
for the selection,

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which includes Iconize
as one of the items in the menu.

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In a program with expressions
that have already been iconized,

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there are several ways to see
the original expressions,

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one of which
is to click the button

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with the plus sign
in the iconize form

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and choose Uniconize.

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As already noted,
iconized forms like this

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are especially useful
for larger programs,

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where the iconized forms
provide a nice way to manage

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long blocks of code,
as small labeled pieces.

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There are many other features
to help with programming

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that go beyond the features
that were covered in the section.

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Often just clicking a button
that pops up

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is a good way
to find useful features.

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For example, the error message
from this input

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gives a button that you can click
to open a Stack Trace

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to see where
the message came from,

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which can be useful
for debugging.

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Also the focus in this section
is on Wolfram Notebooks,

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but there are
many programming tools

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that are part of the underlying
computation engine.

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For example,
the Echo function in this input

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shows an easy way to monitor
the progress of a calculation.

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That's the end of the examples
for this section.

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For the features that were
covered in this section,

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you can find more information
in the Wolfram Documentation,

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and in particular, you can find
more information about syntax,

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coloring, bracket matching
and related topics

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in this tutorial on using
the Input Assistant.