How deeply does The Well-Grounded Rubyist, Fourth Edition cover else clause?

Explains branch ordering, elsif cascading, and nil when no fallback exists.

Else clause

As explained in The Well-Grounded Rubyist, Fourth Edition

The else keyword introduces the alternative branch of a conditional statement when preceding conditions do not succeed.

An else clause supplies the fallback branch of an if statement. Ruby executes it only when the if condition and every preceding elsif condition fail. section 6.1.1

if condition
  # code executed if condition is true
else
  # code executed if condition is false
end

Use else to separate the code for a true condition from the code for every false case. section 6.1.1

Branch selection follows a fixed order:

Ruby executes the first successful if or elsif branch and ignores the remaining branches. section 6.1.1
Ruby executes else when none of the preceding tests evaluates as true. section 6.1.1
Ruby returns nil when all conditions fail and no else clause exists. section 6.1.1

Classifying a number

An if/elsif/else chain prints whether an entered integer is positive, negative, or zero; else handles the remaining case.

How The Well-Grounded Rubyist, Fourth Edition covers it

Cover of The Well-Grounded Rubyist, Fourth Edition

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Also explained in

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Python How-ToAn else clause is an optional part of a Python try...except statement that runs when the protected try clause completes without raising an exception.
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Get Programming: Learn to code with Python
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The Quick Python Book, Fourth EditionAn else clause is the optional part of a try statement that executes only when its try block completes without raising an exception.
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Learn SQL in a Month of LunchesELSE is a procedural SQL control-flow keyword that introduces the fallback branch executed when preceding conditions are not satisfied.

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Related concepts

conditional logicpart of · Conditional logic is a programming technique that selects execution paths, actions, or result values according to evaluated conditions.
try-catch statementpart of · A try-catch statement is a control-flow construct that executes code under exception handling and transfers control to a matching handler when an exception is raised.
loopuses · A loop is a programming control-flow construct that repeatedly executes a block of instructions according to an iteration rule or continuation condition.
return statementcontrasts with · A return statement ends the current function or routine invocation and optionally supplies its result to the caller.
literaluses · A literal is a language construct that directly denotes a fixed value or specifies an exact value permitted by a type.

This explainer was generated by Manning's knowledge graph from the text of The Well-Grounded Rubyist, Fourth Edition. The section links point to the parts of the book it draws on.