SYNTAX ERROR: Difference between revisions

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A SYNTAX ERROR is an [[error message]] which indicates that a rule of [[APL syntax]] was violated. A SYNTAX ERROR may indicate an ill-formed expression which violates APL's grammar:
A SYNTAX ERROR is an [[error message]] which indicates that a rule of [[APL syntax]] was violated. A SYNTAX ERROR may indicate an ill-formed expression which violates APL's grammar:
<source lang=apl>
<syntaxhighlight lang=apl>
       (
       (
SYNTAX ERROR
SYNTAX ERROR
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</syntaxhighlight>
</syntaxhighlight>
However, a SYNTAX ERROR may also indicate a problem not with the sequence of tokens in a statement, but with their meaning. For example, below an error results when a [[function]] is called with invalid [[valence]]: here, a [[monadic function]] with two arguments.
However, a SYNTAX ERROR may also indicate a problem not with the sequence of tokens in a statement, but with their meaning. For example, below an error results when a [[function]] is called with invalid [[valence]]: here, a [[monadic function]] with two arguments.
<source lang=apl>
<syntaxhighlight lang=apl>
       fn ← +
       fn ← +
       2 fn 3
       2 fn 3
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         ∧
         ∧
</syntaxhighlight>
</syntaxhighlight>
Depending on the value of <source lang=apl inline>fn</syntaxhighlight>, the same statement may or may not be considered invalid syntax. This is to be expected, since APL does not have a [[wikipedia:context-free grammar|context-free grammar]] and needs to know the type of each variable to parse a statement.
Depending on the value of <syntaxhighlight lang=apl inline>fn</syntaxhighlight>, the same statement may or may not be considered invalid syntax. This is to be expected, since APL does not have a [[wikipedia:context-free grammar|context-free grammar]] and needs to know the type of each variable to parse a statement.


{{APL features}}[[Category:Errors]]
{{APL features}}[[Category:Errors]]

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